Taking tomato variety‘ Jingcai No. 6’ as test material，this paper studied the effects of different cultivation densities（CD）（3.8，5.0 plants · m^-2）and ion treatments（IT）（K⁺，Na⁺） on plant growth，fruit yield and fruit quality of substrate-cultivated tomato，and constructed TQI（tomato quality index）that could be used to comprehensively evaluate tomato fruit quality．The results showed that raising K⁺ concentration in nutrient solution could increase the contents of soluble sugar，soluble solid，sugar-to-acid ratio（SAR）and VC in the second tomato fruit set，without influencing tomato yield．Although cultivation density（CD） had no significant influence on tomato yield and quality，the content of organic acid and nitrite and SAR of the first tomato fruit set was significantly affected by CD×IT interaction．In addition，the second fruit set was the key for producing high quality tomato，and it showed the highest TQI when 3.8 plants · m^-2 combined with K+-rich nutrient solution．Taken together，it is suggested that in actual production controlling CD at 3.8 plants · m-2 and adopting irrigation with K⁺-rich nutrient solution could obtain high quality tomato and yet receive stable yield．