“3414” fertilizer experiment was actualized to research the effect of nitrogen,phosphorus and potassium fertilizers on tomato in protected cultivation.The results showed that,the suitable application of N,P,K fertilizers increased tomato yield,but excessive application reduced the yield.The effect of K fertilizer on yield was greater than those of N and P fertilizers.Combined fertilization of N and K or P and K increased tomato yield,but combined of N and P fertilizer reduced production.The nitrogen,phosphorus(P2O5)and potassium(K2O)application rates for optimum economic fertilizing were 119.0,50.4 and 375.6 kg/hm2,respectively,and the ratio was 1∶0.42∶3.16.Effects of different N levels on tomato nitrate and nitrite contents were not regularly.Nitrate content of tomato was increased firstly and then decreased when the P and K application increased;but the content of nitrate and nitrite of tomato fruits decreased when NP and PK fertilizer were applied.The soluble sugar contents in tomato fruits increased in NK and PK fertilizer treatments.The total acid contents of tomato fruits decreased in NP and PK fertilizer treatments,but increased in NK fertilizer treatment.The content of Vc in tomato fruits was increased in both NK and PK fertilizer treatments.Nitrogen,phosphorus,potassium fertilizer combined application played an important role in improving the yield and quality of tomato.