Open field nighttime warming system was designed to investigate the effects of longterm nighttime warming and successive notillage on inorganic nitrogen(N)and mineralization and nitrification rates in the cropland soil.The experiments were conducted with four treatments: normal nighttime temperature with traditional tillage(CK)，nighttime warming with traditional tillage(W)，normal nighttime temperature with notillage(NT)，and nighttime warming with notillage(WNT).Compared to CK，alkalihydrolyzable N and ammonium N remarkably increased under W treatment，which were increased by 26%~28% and 82%~133%，respectively in January and February.In the incubation experiments，mineralization and nitrification rates increased significantly in warming treatments.Under NT treatment，soil average alkalihydrolyzable N and ammonium N contents were increased by 15% and 41%，respectively than those of CK，while mineralization rate was significantly highter and nitrification rate was significantly lower in NT than those in CK and W treatments.For WNT treatment，mineralization rate was higher than that in NT treatment，nitrification rate was lower than those in CK and W treatments.Thus，it was concluded that notillage could facilitate mineralization process of organic N in cropland soil，inhibit nitrification process，and hence reduce the risk of N loss.