To evaluate the molluscicidal effect of 26% suspension concentrate of metaldehyde and niclosamide (MNSC) in the fields of mountainous areas in Yunnan Province.Some representative Oncomelania snail environments of schistosomiasis endemic regions were selected as study areas in Heqing County, Yunnan Province and 26% MNSC and 50% wettable powder of niclosamide ethanolamine salt (WPN) were used to kill the snails with the mechanical spraying and sprinkler spraying methods respectively.Seven, 15, 30 days after the spraying with the mechanical spraying method, in corn fields, the snail mortality rates were from 88.68% to 92.88% in the MNSC group, and from 89.86% to 90.32% in the WPN group respectively, and in the ditch, the snail mortality rates were from 89.97% to 94.46% in the MNSC group and from 90.08% to 96.74% in the WPN group respectively, and there was no significant difference between the 2 groups (P > 0.05); 7, 15, 30 days after the spraying with the sprinkler spraying method, in corn fields, the snail mortality rates were from 66.14% to 89.11% in the MNSC group, and from 78.40% to 91.22% in the WPN group, respectively, in the ditch, the snail mortality rates were from 84.13% to 94.27% in the MNSC group, and from 85.81% to 95.26% in the WPN group respectively, and there was no significant difference between the 2 groups (P > 0.05).26% MNSC has good molluscicidal effect in the fields of mountainous areas in Yunnan Province