Abstract: Effects of different nitrogen, phosphorus and potassium ratios combination with complex nitrification inhibitors on the yield, nitrate content and nutrient forms of lettuce(Lactuca saliva L. ) were studied in three acid garden soils under field experiment condition. The results indicated that the yield of lettuce was in the order of little acid soil > acid soil > strong acid soil. In acid and strong acid soil, the yield of lettuce was significant increased by 6.2%-18.2% , but decreased in little acid soil. The nitrate contents of lettuce stem and leaf were decreased by 25.1%-76.3% and 3.1%-27.7% (except in little acid soil) in HNK treatment (high rate of N and K fertilizers) combination with complex nitrification inhibitors. The effect was stem > leaf and the HNK + C2 (complex nitrification inhibitor No. 2) treatment was best. The nitrate content of lettuce leaf in three soils was acid soil>little acid soil>strong acid soil, and nitrate content of lettuce stem was highest in acid soil. The nutrient forms of N, P, and K in lettuce leaf were mainly protein N, non - protein P and non - protein K. The ratio of protein N to total N, protein P to total P, protein K to total K was increased in HNK + C1 (complex nitrification inhibitor No. 1) and HNK + C2 treatments. There were significant negative correlations between nitrate content and total N, protein N, total P, protein P, protein K of lettuce leaf.