Abstarct: Nitrate content is one of the important factors in determining the quality of vegetables. Nitrate accumulation, which occurs mostly in vessels, petioles and leaves, can have an adverse effect on human health. In an experiment conducted at the Faculty of Agriculture of Shahroud University of Technology, the amount of nitrate in greenhouse tomatoes under the influence of nitrogen and potassium fertilizers was investigated. Experimental factors included potassium at 3 levels: (15, 45 and 60 mg per plant and nitrogen at 7 levels including (15, 30, 45, 60, 75, 90 and 105 mg per plant). After plant growth and foliar application, samples were collected and morphological traits including number of plants per panicle, number of fruits per panicle, plant height, stem diameter and fruit weight were measured. Nitrogen treatment had a positive effect on fruit weight, so that the lowest weight was related to treatment 15 and the highest was related to treatment 105 with numbers of 227 and 293. respectively, no significant difference was observed in stem diameter and stem height. Clusters per plant were also examined and there was a significant difference between concentrations of 15ٌ, 30 and 45. Regarding the number of fruits in the cluster from 30 to 105, the number increased significantly from 4.8 to 6.4. Potassium fertilizer treatment had a significant effect on treatment 45. The number of fruits and number of spikes in different potassium treatments did not differ significantly.Plant height increased from 277 to 281 cm at concentrations of 15 and 60. Stem diameter and fruit weight At concentrations of 15 and 30 There was no significant difference. While with treatment 45 they were significantly different. Nitrogen treatment had an effect on fruit nitrate concentration so that 15 and 105 concentrations with 45 and 81 ppm, respectively, had the lowest and highest nitrate concentrations. There was no significant difference between fruit and leaf potassium in different concentrations and only differences in treatments 15 and 105 were observed and increased. Fruit nitrogen and leaf nitrogen also increased. Fruit nitrogen was from 3.9 to 4.6% in the lowest and highest treatment. Leaf nitrogen increased from 3.9 to 4.7% in treatment 30 to 105. Of course, it should be noted that there was no significant difference between the 90 and 105 treatments, so it is better to use the 90 concentration. Nitrogen fertilizer had a significant effect on chlorophyll b and a and its rate increased from 3.9 at 30 to 4.6 mg / g at 105. Chlorophyll a also increased from 11 in treatment 30 to 17 mg in treatment 105. Total chlorophyll under nitrogen treatment increased significantly, from 14.9 at a concentration of 30 mg to 24.4 mg / g at a concentration of 105. Regarding the treatment of potassium fertilizer, the amount of nitrogen and potassium in leaves and fruits did not differ significantly in different treatments. However, there was a slight difference between chlorophyll a and b, while a significant increase was observed in total chlorophyll, from 19.4 to 20 mg / g at a concentration of 15 to 45 mg per plant. Nitrogen fertilizer yield was such that nitrogen concentration was increased by 0.003 ppm per mg of fertilizer. In the case of potassium, the high amount of nitrate in this plant can be related to the high consumption of nitrogen fertilizers, agronomic factors and other environmental factors. It is suggested that the nitrate of tomatoes consumed in different seasons of the year be randomly evaluated and their nitrate content be controlled.