The effect of the combination of nitrogen and potassium fertilizers on yield and quality of lettuces (Kexing No. 3 and Doubletip lettuce) in two kinds of soils were studied by the field experiment. The results showed that there was significant difference between the yields of two lettuces. To the acid soil, the CK treatment(N¹⁵K¹⁰) was the best to gain the high yield of lettuces, but nitrogenous fertilizer could be reduced appropriately for Doubletip lettuce in the alkali soil. The yields of two lettuces in the alkali soil were higher than in the acid one. Decreasing nitrogen or increasing potassium fertilizer reduced the content of nitrate of lettuces. The nitrate content was higher in stem than leaf in harvest anaphase, and higher in acidic soil than in alkali one. The effect of nitrogen and potassium fertilizers on nutrient quality of two lettuces were different, increasing potassium or nitrogenous fertilizer was more effective in acid soil than in alkali one. The contents of Vc in two lettuces were higher in leaf than in stem, higher in acidic soil than in alkali soil. The contents of soluble sugar in two lettuces were higher in acidic soil than in alkali soil except the stem of Doubletip lettuce in increasing K treat. The contents of amino acid in two lettuces were higher in stem than leaf.