The large amount of chemical fertilizer applied in protected vegetable soil in China has caused a lot of N2O and NH3 losses. The substitution of organic fertilizer for part of chemical fertilizer is an effective measure to realize the recycling of nutrient resources in the planting and breeding system, and to reduce the application of chemical fertilizers and their environmental losses. In this study, a protected vegetable soil with Chinese cabbage planting in the suburbs of Changsha was taken as the research object. In the protected vegetable soil, a plot experiment was conducted to plant milk cabbage. The field experiment was conducted with four treatments: non-fertilization (CK), conventional fertilization (CON), 30% N from cow manure organic fertilizer + 70% from chemical fertilizer (CM), and 30% N from chicken manure organic fertilizer + 70% from chemical fertilizer (NM). The emissions of nitrous oxide and ammonia volatilization during the growing season of Chinese cabbage were measured by static chamber method and closed chamber intermittent extraction method, respectively. The aims of the study were to explore the emission reduction effects of organic-inorganic fertilizer combined application on N2O emissions and NH3 volatilization, and to clarify the influencing factors. The results showed that compared with conventional fertilization, N2O emissions from CM and NM treatments decreased by 38.5% and 33.1% respectively, while NH3 volatilization from CM and NM decreased by 8.5% and 19.4% respectively. The total warming potential of nitrous oxide and ammonia volatilization in CM and NM treatments decreased by 38.4% and 33.0%, respectively. Among the two organic fertilizer treatments, the ammonia volatilization of NM treatment was significantly lower than that of CM treatment, with a decrease of 11.9%. N2O emissions and ammonia volatilization daily fluxes was positively and significantly correlated with soil temperature. N2O emissions and ammonia volatilization daily fluxes of CON and NM treatments was positively correlated with soil ammonium nitrogen, while N2O emissions of CON treatment was positively correlated with soil nitrate nitrogen only. Compared with CON treatment, the nitrogen fertilizer utilization efficiency of CM and NM treatment increased by 26.8% and 41.5%, respectively, with no significant difference in yields. Therefore, combined application of organic fertilizer and chemical fertilizer can reduce N2O and NH3 emissions as well as stabilize yields in the protected vegetable production systems, which is of great significance to reduce greenhouse gases emissions from vegetable production.