On August 16，2016，it was reported that some sheep died of unknown reasons in a township in Wenquan County of Xinjiang，which was suspected to be an outbreak of Haemonchus contortus infection. In order to find out relevant causes，control any spreading，reduce any loss and avoid recurrence of any such cases，relevant staff was organized by Xinjiang Uygur Autonomous Region Center for Animal Disease Prevention and Control to conduct an emergency epidemiological investigation by means of on-site interview，field investigation，questionnaire investigation and clinical autopsy. It was investigated that the pastoral area in the county was a historically infected zone with Haemonchus contortus，where a large number of grazing sheep died due to wide infection with the disease decades ago. A favorable external environment for large amount of Haemonchus contortus reproduction was provided by continuous cloudy and rainy weather under appropriate temperature since July to Mid August 2016，which was the external factor for such outbreak，while grazing on the same grassland with abundant water and grass，failure to timely carry out epidemiological investigation and to accurately find out the causes for targeted prevention and control also contributed to the occurrence and spreading of the outbreak. According to the above results，it was recommended to prevent and control the disease through scientific grazing，rational administration and deeply-buried processing of sheep feces.