In order to understand the changes of nitrogen compounds in root bleeding sap during the genetic improvement of soybean varieties, 29 soybean varieties bred in Jilin Province during 1923- 2009 were used to measure the concentration and total amount of nitrate, amide and free amino acids (FAA) in root bleeding sap at different growth stages. The result showed that there were great amount of FAA in soybean root bleeding sap; the concentration, total amount of nitrate and FAA increased with genetic improvement of soybeans cultivars, while the amide concentration decreased and the change of the total amount was not significant with year of release. Nitrogen concentration in root bleeding sap of the same soybean variety decreased with the proceeding of growth stage. The maximum total nitrogen amount was at R4 stage, the second was at R2 stage and the minimum was at R6 stage. It was concluded that genetic improvement of soybean varieties improved the level of nitrogen compounds in root bleeding sap, and nitrogen metabolism was the most vigorous at R2 stage. R2 stage was the critical period requiring extra nitrogen and the nitrogen fertilizer should be applied at this time.