Background: Forest musk deer (Moschus berezovskii) is a national first-level protected and endangered wild animals in China. The intestinal coccidiosis of captive forest musk deer is one of the most important diseases. However, few studies have been conducted to quantify Eimeria sp. infection and to identify its molecules. Thus, the objective of this study was to investigate the Eimeria sp. infection in the intestinal tract of forest musk deer in Sichuan and Shaanxi, China, and to identify the 18S rRNA gene fragment of Eimeria sp. , which provides scientific basic experimental data for the molecular epidemiological investigation and population genetic analysis of Eimeria sp. of captive forest musk deer in 7 regions.Methods: 328 faecal samples of forest musk deer were collected from 7 farms. The DNA of Eimeria sp. in the positive samples was extracted and used as template for nested PCR amplification. The 18S rRNA gene fragment was connected with the plasmid vector, and the products were introduced into Escherichia coli (DH5α). The culture bacterial solution was used as a PCR reaction template for identification.Results: In total, we collected 328 faecal samples from forest musk deer in Lixian (n=54), Maoxian (n=52), Ma’erkang (n=49), Dujiangyan (n=55), Hanyuan (n=41), Luding (n=36) and Weinan (n=41). 198 (60.37%) faecal samples were positive for Eimeria sp. We analyzed the 18S rRNA gene sequence of Eimeria sp, and determined 34 types with similarity of 90.5% ~ 100%. A phylogenetic tree constructed based on the 18S rRNA gene sequence of Eimeria sp., it was confirmed that Eimeria sp. parasitized in the intestinal tract of forest musk deer was closely related to Eimeria alabamensis from Bos taurus, Eimeria faurei from Ovis aries and Eimeria ahsata from Ovis aries.Conclusions: To our knowledge, this was the first molecular identification of Eimeria sp. in the intestinal tract of forest musk deer. The study suggested that Eimeria sp. parasitizes in the intestinal tract of forest musk deer, which is their carrier.