Abstract: The allelopathic effect of leaf extracts on different planting mulch grasses Paspalum wettsteinii, Paspalum notatum, Arachis pintoi, Chamaecrista rotundifolia of general used in Soil and Water Conservation ,on the seed germination and seedling growth of radish,was investigated by bioassay method. The germination rate of radish was very significant inhibition under the treatment of high concentration leaf extract of Paspalum notatum and Arachis pintoi.The inhibition effect of Arachis pintoi reached extremely significant level than the treatmenm of Paspalum notatum and Arachis pintoi. The leaf extract of different planting mulch grasses had significant effect on length of radish root,under the concentrations of 7.5％and 10.0％,the treatment of Arachis pintoi promoted the increating of dry weight of root , the other three treatments all inhibited the increating of dry weight of root and there was significant difference between the treatments of Paspalum notatum and Arachis pintoi. The all leaf extract of four planting mulch grasses promoted the growth of radish seedling under the concentration of 10.0％,and the treatments between Chamaecrista rotundifolia and Paspalum notatum had extremely significant differences.There were not significant effect to the dry weight of seedlings and plants.