Fertilization including fertilizer type，amount and applying manner directly affects the intensity of soil nitrogen supply and crop growth.A field experiment was conducted to study the effects of different fertilizations on the varieties of soil water-soluble nitrogen and their relation to crop grain yields with a rice-wheat rotation. There were five treatments，including non-fertilization (CK)，farmer practice (FP)，local recommended fertilization (LRF)，commercial organic manure partially replaced chemical fertilizer (RF-OM)，straw partially replaced chemical fertilizer (RF-S)，and each treatment had four replications.The results indicated that the contents of soil water-soluble total nitrogen and nitrate nitrogen of RF-OM and RF-S treatments were significantly higher than those of LRF treatment at the young panicle differentiation stage of rice (P<0.05)，and similar to those of FP treatment.At the returning green stage of rice，the contents of soil water-soluble nitrogen (total nitrogen，ammonium nitrogen and nitrate nitrogen) of RF-OM and RF-S treatments were slightly lower than those of LRF or FP treatment，and the differences were not significant.At the jointing stage or full heading stage of wheat，the contents of soil water-soluble total nitrogen and nitrate nitrogen of RF-OM and RF-S treatments were significantly higher than those of LRF treatment (P<0.05).The differences of soil ammonium nitrogen content among four fertilization treatments at each main growth stage of wheat were not significant.Based on reducing nitrogen and phosphorus doses as well as increasing potassium doses，rice grain yields of RF-OM treatment were significantly higher than those of LRF treatment (P<0.05)，and rice grain yields of RF-OM and RF-S treatments were similar to that of FP treatment.Compared with LRF treatment，wheat grain yields of RF-OM treatment were higher，which were reduced of RF-S treatment but the difference did not reach a significant level.It was also found that the rice grain yields were positively significantly correlated to the contents of soil water-soluble total nitrogen and ammonium nitrogen at the returning green stage of rice (P<0.01)，with the correlation coefficients of 0.932 and 0.974 respectively.And so were to the contents of water-soluble nitrogen (total nitrogen，ammonium nitrogen and nitrate nitrogen) at young panicle differentiation stage of rice，and the correlation coefficients were 0.888，0.961 and 0.776.The wheat grain yields were positively significantly correlated to the content of soil water-soluble nitrogen (total nitrogen，ammonium nitrogen and nitrate nitrogen) at each main growth stage of wheat (P<0.01)，and the correlation coefficients were 0.928～0.960，0.827～0.968 and 0.574～0.929.It is particularly notable that the supply of soil water-soluble total nitrogen is much contributive to rice or wheat grain yields.Organic manure applied as a partial substitute for chemical fertilizers，especially the commercial organic manure partially replaced chemical fertilizers could maintain or increase the content of soil water-soluble nitrogen，as well as stabilize rice and wheat grain yields on the basis of reducing total nutrient inputs.