‘Tianxi No.3’ and ‘Bikang T608’ tomatoes were grown under the monopoly with film，with the normal amount of organic fertilizer (60 t/hm²，4M)，the increased amount of organic fertilizer (120 t/hm²，8M)，the recommended amount of nitrogen and potassium fertilizer (225 kg/hm²，N1)，the reduced amount of nitrogen and potassium fertilizer by 15% (191.25 kg/hm²，N2)，and 30% reduction of nitrogen and potassium fertilizer (157.5 kg/hm²，N3)，both of which were randomized completely.And six treatments were set up in total (4MN1，4MN2，4MN3，8MN1，8MN2，8MN3) to investigate the effects of nitrogen and potassium fertilizer reduction and organic fertilizer increase on the quality of tomatoes，and to further quantify the appropriate fertilization gradient.The results showed as follows:(1) The single fruit weight of two tomato varieties increased after increasing organic fertilizer application.(2) At the normal organic fertilizer treatment，the fruit quality indexes of the two tomato varieties varied with nitrogen and potassium fertilizer reduction，indicating that nitrogen and potassium played different roles in different quality indexes.With the increase of organic fertilizer application，the quality indexes (lycopene，Vitamin C，soluble sugar，etc.) of the two tomato varieties basically tended to increase and then decrease with the increase of the reduction of nitrogen and potassium fertilization.(3) The reduction of nitrogen and potassium fertilization in ‘Tianxi No.3’ tomato under the same amount of organic fertilizer treatment increased the nitrogen and potassium contents of the fruits，and the phosphorus content tended to decrease and then increase；For ‘Bikang T608’ tomato，the content of nitrogen increased and the content of phosphorus decreased under the same amount of organic fertilizer treatment.The content of potassium decreased under the normal organic fertilizer treatment，while the content of potassium increased under the increased organic fertilizer treatment.In addition，the tomato quality indicators were analyzed by principal component analysis and ranked together.The results showed that 4MN3 treatment had the best overall effect on the fruit quality of ‘Tianxi No.3’ tomato；4MN2 treatment had the best overall effect on the fruit quality of ‘Bikang T608’ tomato.