Estrogen is an important hormone that affects muscle development in female animals. Previous studies have shown that estrogen can protect muscle cells from apoptosis by inhibiting the MAPK signaling pathway. However, the molecular mechanisms by which estrogen-induced MAPK signaling regulates myoblast growth and development remain unclear. In this study, RNA-seq was performed on ovariectomized small-tailed Han (OR-STH) sheep and sham surgery small-tailed Han (STH) sheep to analyze the effects of estrogen on muscle growth and development in female animals. There were 8721 differentially expressed circRNAs (DECs), 143 differentially expressed miRNAs (DEMs) and 2238 differentially expressed mRNAs (DEGs) in the longissimus dorsi between the OR-STH and STH groups. Bioinformatics analysis revealed that the differentially expressed gene MAPK15 was significantly enriched in the MAPK signaling pathway, which is important for muscle development. Therefore, we constructed the ceRNA network circFAM171A1/oar-miR-485-5p/MAPK15 and explored its effect on muscle growth and development. The results of the molecular mechanism experiments indicated that circFAM171A1 can sponge oar-miR-485-5p to regulate MAPK15. The addition of the exogenous hormone estradiol (E