Abstract: Effects of trifluraiin on soil microbe and earthworm were studied. The results show that lower concentration (about 0. 5-10.0ppm) of trifluraiin stimulate to the growth of soil bacteria, actiriomycetes, and mould, pure cultures of Rhizobium japonicum and Azotobact er chroococcum,not only the colony number on agar medium being increased .but also the size of that being enlarged and the appearance of that being fast. Trifluraiin inhibited the activity of acetylene reduction of A. chroococcum. when it was added at same time with inoculation A. chroocuccum, however?it stimulated when it was done after A. chroococcum had grown well. It is suggested that soil microbes might use trifluraiin as sole carbon and nitrogen resources. More than 2. 0 ppm of trifluraiin was toxic to earthworm.