Abstract: with the fresh vegetable soybean number 1 as the testing material,the effects of five different levels of density on root growth and yield were studied at the field.The result showed that： With the increase of plant density,the root dry weight,the spatial distribution root quantity,bleeding sap, root activity and yield increased at first and then decreases.But ratio of root/top showed the opposite results.Considering the vegetable soybean fresh pod yield and root system comprehensive characters,the 135 thousands plants per ha treat was proper, yield is 15185.50kg per ha.