Offering sacrifices to heaven and earth is a ritual of the Yi people to pray for good weather, good harvests, and the safety of people and animals. The sacrifice is presided over by Bimo, and the altar is mostly set up on the top of a mountain with a three-tier shape (commonly known as the Mountain of Offerings to Heaven or the Mountain of Santai). There are also artificial three-tier altars. If you pray for wind and rain, the offerings are black cows, sheep or chickens, and if you pray for clear weather, the offerings are white. The "Yunnan Chronicles" of the Ming Dynasty records that "Luoluo, the witch is called Baima, and the folks offer sacrifices to heaven with three steps of the platform, and the white horse prays for it." "Baima" is a transliteration of the Yi priest "Bimo". The Yi people hold a ceremony to offer sacrifices to heaven and earth during the Horse Cherry Blossom Festival in the first month of the year every year. The altar is set up in front of a pine tree about two meters high. A divine platform is built at its root with chestnut branches. The altar is built into a square platform one foot and five inches high with a sala tree. A single-wood ladder is cut and placed on the altar for the gods to be sacrificed, to show that the gods of heaven and earth are connected. A layer of green pine needles is laid on the altar, and five unpolished ox-horn stones are arranged in an east-west direction, representing the five earth gods of the east, south, west, north and center. A pine needle is inserted in front of each of the five earth gods. One liter of rice, a piece of meat and a few banknotes are offered, a bunch of incense is inserted on the rice, and a bowl of wine, tea and clean water are also offered. The altar is made of chestnut branches and arranged in three, six, nine and twelve. They symbolize the gods of heaven and earth in nature and represent auspiciousness. Before the sacrifice, all the required offerings, including the sacrificial animals, must undergo a purification ceremony, that is, red-hot stones are placed under the branches of the horse mulberry tree, the mulberry branches are immersed in water, and evergreen leaves are dipped in water and sprinkled on the stones to let the steam clean the offerings. After going back and forth three times, the offering can be made. Before the sacrifice, the bimo himself must also rinse his mouth, wash his hands and clean his body with holy water from the vinegar jar before he can participate in the sacrifice. All the men, women, old and young in the village climbed up the Jitian Mountain. The sacrifice began at noon. The Bimo presided over the ceremony. All participants knelt in front of the altar in several rows according to their seniority. The main priest Bimo began to ring the bell to pray to the gods of heaven and earth. The sacrificial words were "Today we will sacrifice to heaven, today we will sacrifice to earth, today is the Year of the Snake, the Year of the Snake is an auspicious year, the Year of the Snake will sacrifice to heaven, the Year of the Snake will sacrifice to earth, the Year of the Snake will sacrifice to the sun, the Year of the Snake will sacrifice to the moon, heaven and earth, sun and moon, please come down! Tea, rice, chicken and wine are also offered. Luo Luo is sincere, and sincerely sacrifices to heaven and earth. Today is an auspicious day, and an auspicious day sacrifices to heaven and earth..." The sacrificial words run through the whole process of the sacrifice. The master asks him to bless the health of people and animals, a good harvest, and wealth. At the end of the sacrifice, everyone takes a stick of incense from the altar and takes it back, which can bless their family to be safe and smooth for a year. After offering sacrifices to heaven and earth, Bimo will march in witch steps, lead gourd teams, singing teams, dancing teams, women plowing teams, shaking magic bells, dancing sheng, carrying farm tools to ninety-nine hills and ninety-nine mountain villages, knock on doors from house to house, chant scriptures and pray, and call "Migu, Migu" to send treasures and drive away evil spirits. Each house owner will offer white wine to guests and invite participants to sit on the ground in the courtyard and drink white wine together. After Bimo's prayers, each household will have peace of people and livestock, a good harvest, wealth and good luck in this year. Every household is lucky to have a heaven-offering team come to their home to pray and bless. It can be said that traditional Yi culture promotes unity and harmonious ethnic relations.