From July in 1997 to March in 2000,the writer undertook epidemiological investigation of hypodermiasis to 483 cattle at 15 villages and examined the seasonal fluctuation of infection of each stadium larvae of hypodermiasis to 307 cattle at 21 villages of five counties in Xing'an League,Inner Mongolia.The results of the investigation are as follows:It concluds that the main pathogenes of hypodermiasis in Xing'an League are H.lineatum maggot and H.bovis maggot,and　H.lineatum maggot is the local superior species.The clinical examination has showed that the infection rate of hypodermiasis in Xing'an League was 80.35%,and the average infection intensity was 2～73.Surveillance of each stadium of hypoderma larvae,infection rate was 50%～100%,infection intensity was 1～193.The unique geological environment,the natural condition and the characteristec of cattle husbandry in Xing'an League are the reasons which make hypoderma prevalence in this area.