Objective To understand the Oncomelania hupensis snail distribution in the working areas of Yangtze River hy?drologic agencies located in the middle and lower reaches of the Yangtze River in 2016,so as to provide the evidence for assess?ing the risk of schistosome infection of hydrological workers and establishing the control strategies. Methods The suspicious en?vironments with O. hupensis snails in the above working areas were selected as study areas,and the snail situation was surveyed by the system sampling method combined with the environmental sampling method. The survey data were collected and analyzed statistically. Results Totally 19 working areas from 17 hydrological agencies were selected as the investigation sites,among which,10 working areas from 9 agencies were found with O. hupensis snail distribution. The constituent ratio of the areas with snails reached to 38.81%of the investigation areas,the occurrence rate of frames with snails was 3.08%,and the average densi?ty of living snails was 0.07/0.1 m2. By comparison,the average density of living snails and occurrence rate of frames with snails in hydrological agencies under the jurisdiction of the Middle Reaches Administrative Bureau were the most serious among three administrative bureaus of the Yangtze River Water Resources Commission. Conclusions There are various degrees of O. hupen?sis breeding in the working areas of hydrological agencies located in the middle and lower reaches of the Yangtze River ,and the hydrological workers are facing with the risk of schistosome infection.