Abstract: Field experiment was conducted to study the optimum application rate of N and K fertilizer on the growth and yield of spring wheat under drip irrigation in an arid area of Northwest China. Four nitrogen fertilizer treatments (0, 80, 160, 240 kg/hm²) and four potassium fertilizer treatments (0, 88, 176, 264 kg/hm²) were set up. The results showed that, increasing application of nitrogen and potassium fertilizer at low level could promote the growth of spring wheat to some extent, but overuse of fertilizer might inhibit its growth. The combination of nitrogen and potassium fertilizer could increase the yield of spring wheat significantly. The average yield in N0 treatments was 5813 kg/hm². In contrast, the average yield in N1 treatments was 6563 kg/hm², which was 10.6%- 15.3% higher compared to the control treatment. The average yield in N2 treatments was 7025 kg/hm² which was 19.1%-22.5% higher compared to the control treatment under identical potassium fertilizer (K2O 176 kg/hm²) and phosphatic fertilizer (P2O5 60 kg/hm²) level. There was no significant difference in yields among treatments under different potassium fertilizer levels. However, there was moderate increase of yield with increase of K fertilizer which present parabolic trend under identical N and P level. The optimal application of nitrogen and potassium fertilizers under drip irrigation was recommended primarily as N 150-160 kg/hm² and K2O 88 kg/hm².