Abstract: Conventional fertilization and irrigation management caused soil nitrogen leaching loss and low fertilizer use efficiency in greenhouse vegetable growing system. In order to evaluate the effects of different fertilization on vegetable yield, nutrients uptake, dynamics of leachate and nitrogen leaching, and simultaneously determine how much nitrogen lost by leaching and the ratio of leaching N/fertilizer N. A field experiment with six treatments (no fertilizer, manure, conventional fertilization, optimal fertilization, conventional fertilization + regulating soil C/N and optimal fertilization + regulating soil C/N; represented by CK, M, CON, OPT, CON+C/N and OPT+C/N, respectively.) was carried out in greenhouse tomato and cucumber growing system in Yellow River Irrigated region of Ningxia. The experimental design was the randomized complete block with three replications; each plot was 23.4 m2 (6 m 3.9 m). The results indicated that the difference of fruit yield between treatment CON and OPT was not significant in tomato and cucumber season, nutrients uptake was KNP. Both of N and P fertilizer use efficiency was less than 7%, and the maximal K fertilizer use efficiency was 12.3% in two season vegetables. Nitrogen leaching was related to fertilization, irrigation and vegetable growing stage, and nitrogen leaching losses from soil in cucumber season was greater than that in tomato season under the same fertilization management practice. NO3--N leaching loss accounted for more than 70% of total nitrogen leaching in both vegetable growing season. The ratio of total leaching N/fertilizer N and NO3--N/fertilizer N in tomato season was 2.95%~6.65% and 2.50%~5.56%, respectively; and thatof in cucumber season was 3.40%～6.96% and 2.89%～5.70%, respectively. The ratio of leached NH4+-N/fertilizer N was far less than 1% in tomato or cucumber season. By reducing nitrogen rate and application of high C/N ratio manure or crop straw to regulate soil C/N ratio was benefit to decrease nitrogen leaching losses in greenhouse tomato-cucumber growing system.