Abstract: The movement and the distribution of ³⁵S-dimehypo in model terrestrial-aquatic ecosystemwere studied using model ecosystem experimental equipment and radioisotope tracer techniques. In model ecosystem composed of rice plant-soil-water, ³⁵S-dimehypo applied in field water moved mainly by irritating water during the experiment for 58 days.The recovery from soil leakage was 51.39% of dose. 35S-Dimehypo was absorbed by rice roots. The resid ues were 5.94% in whole plant (0.32ppm in shoot and l.lSppm in roots) and 18.48%(about 0.01ppm)in soil .In model ecosystem including water .(collected from soil leakage ) -Azolla (Wolffia arrhiza Wimm) -fish (grass carp, Ctenophryngodon idellus)-sna.\\, high absorption of 35S-dimehypo by Wolffia arrhiza Wimm was found during the experiment for 29 days .The accumulation ratio was 17.67% and higher than those of snail meat (10.47%)and homogenized fish(4.29%). In fish, the accumulation ratio of parts differed :viscera(6.67%) > gill(I.24%) > bone(.1.07%) >meat(0.56%). Very low bioaccumulation appeared.