In order to optimize the amount of potassium application of facility vegetables in Hetian，maintain soil nutrient balance，and continuously improve the planting benefits of local facility vegetables，the effect of potassium application on the growth，yield and quality of tomato in Hetian solar greenhouse was studied. There were 4 treatments in the experiment，amount of potassium fertilizer applied during the whole growth period were 0，288，360 and 432 kg/hm²，respectively. The test results showed that potassium application had no significant effect on tomato plant height and stem thickness. Among the different amount of potassium application，leaf area index，leaf SPAD value，the weight of single fruit and the content of soluble sugar reached the maximum when potassium application amount was 288 kg/hm². Tomato yield and fruit Vc content reached the highest value when the potassium application content was 360 kg/hm². The soluble solids and hardness reached the maximum when the potassium application content was 432 kg/hm². Through the comprehensive evaluation of yield and quality by CRITIC method，it was finally evaluated that the optimal of potassium application amount was 360 kg/hm²，so it was suggested that the potassium application amount of facility tomato in the whole growth period that similar to the experimental conditions in Hetian area was 360 kg/hm².