Abstract:In order to understand the effects of different nitrogen levels on lettuce growth and qualities, the threedimensional pipeline cultivation system, suitable for vegetables hydroponics, was designed independently and produced, nutrient solution of NO3-: NH4+ = 10:0, NO3-: NH4+ = 7:1, NO3-: NH4+ = 7:3 were prepared, respectively, and then cultivation effects of lettuce (Lactuca sativa L.) under different nitrogen levels were comprehensively evaluated by using fuzzy mathematics theory, and the analytic hierarchy process (AHP) to determine the weights of lettuce quality. The results showed that cultivation effect was the best with nutrient solution of NO3-: NH4+ = 7:3, followed by NO3-: NH4+ = 7:1. Cultured with NO3-: NH4+ = 7:3, the yield of lettuce, contents of chlorophyll, soluble sugar, soluble protein in leaves were the highest, and nitrate content was at least, so that the comprehensive quality was the best. Therefore, AHP has a better applicability for synthetically evaluate the cultivation effect of lettuce under different nitrogen levels, which helps to get the optimum nutrient solution in south facility pipeline for lettuce cultivation.