Abstract: The biomass changes of Com.Zizania latifolia was studied using the harvest method,and its primary production was estimated.The peak shoot density of the community,occuring in March 23 1990, was 97.8/m².The peak standing crop 1520.88 g/m² was achieved in September.The cumulative weights of the dead leaves during March and June was reckoned using the productive structure graphs,and according to the method of Mason and Bryant(1975),the production of the community was estimated as 1792.02g/m²,17.8% higher than its peak standing crop,and P/B=1.24.The seed production of the community was very low,only about 14.46g/m².