Abstract:During the growth of tomato over the winter in greenhouse, the crop needs more nitrogen and potassium fertilizers than phosphorus fertilizer, and a proper N:K ratio in fertilization is very important for the crop. An experiment was carried out on sequential top dressings different in N:K ratio to determine their effects on fruit setting and quality of the fruits of tomato growing over the winter in greenhouse. Two treatments were both designed to have 11 top dressings. Treatment One, as control, had a fixed N:K ratio (N:K2O=1:1.2) and Treatment Two varied ones, i.e. 3 top dressings (N:K2O=1:1) at the fruit-setting stage, 3 (N:K2O=1:1.2) at the initial harvesting stage, 3 (N:K2O=t:1.4) at the mid-harvesting stage, and 2 (N:K2O=1:1.2) at the late harvesting stage. Results showed that the two treatments differed slightly in plant shape indices, e.g. stem diameter, and in total number of fruit tassels, but Treatment Two had a bigger number of effective fruit tassels. During the harvesting season, Treatment Two significantly increased the number of fruits set and single fruit weight, which resulted in a significant increase in tomato yield. The two treatments did not differ much in their effects on fruit quality at the initial harvesting stage, but did significantly at the late harvesting stage, especially in terms of Vc content in fruit. The fruits harvested at the late stage were found to be higher than the ones harvested at the initial harvesting stage in all the quality indices.