Abstract: The summer soybeans`yield is about 2400kg/hm2 in YuDong Plain . It has adopted six plant growth regulators such as 784-1,unicontanol ,4-iodophenxyacetic acid ,sodium bisulfite ,No．5 ABT Root Powder and 1 –triacontanol and so on .The rate of individual seedless relatively reduces 7.7%-45.6%.The weight of the individual raises 1.2-2.7g．The plant growth regulators which can not only reduce pods without peas but also raise the yield obviously are 1-triaontanol, 784-1 and No.5 ABT Root Powder. Their physiochemical and biological effects are : The roots grow strong, the roots` suck improves; The quantity of root Nodule improves, the activations of nitrate reductase and nitrogenase respectively raise 66.2%-89.3% and 29.0%-39.9%; The chlorophyll content of leaf blade raises 2.81-3.08 mg/g, The photosynthetic rate (CO2) strenghten 25.2~27.3 mg/（dm2·h）; The soybean yield increases 12.3%-14.7%.