The split_plot experiment was conducted to study the effects of PP333 on the growth and development of narrow_leaf soybean variety_Zhongduo 29.The populations were planted in different density,and the liquid contained 80 mk/kg PP333 was sprinkled oh those populations in different growing periods.The results showed that leafing speed,knot number,100 seeds weight,dry weight of leaf,branch number and total pod number weren't changed significantly,but the height of plant and stem weight were decreased,weight ratio of root to stem in flowering period and perfectly developed seed number were increased,so a high yield could be expected. study on interaction between PP333 and population density showed that soybean yield was increased by sprinkling PP333 on high density population in flowering period.