The effects of different contents of potassium humate (0,0.01%,0.1%,0.3%,0.5%) on the yield,physiological characteristics and nutrient absorption and utilization of pakchoi ‘Siyueman’ （Brassica chinensis） are studied with pot experiments. The result showed that potassium humate significantly increased the yield of pakchoi,with the highest yield at dosage of 0.1% potassium humate,37.1% higher than that of the control. MDA content and antioxidant enzyme activity was changed. In addition,the content of N,P and K increased with the application of potassium humate in pakchoi,among them N and K enhanced significantly. The total accumulation of N,P and K increased first and then decreased,with the largest dosage of 0.1%,increased by 56.4%,37.3%, and 50.7%,respectively.The absorption efficiency (AE),partial factor productivity (PFP) and dry matter efficiency (DME) of N,P was significantly improved,with the promoting effect being the best at dosage of 0.1%. N increased by 55.6%,42.2% and 42.2%,respectively ; P increased by 40.0%,40.0%,30.0%,respectively. When the content of potassium humate was 0.01% and 0.1%,the AE,PFP and DME of K are higher than that of control. When the dosage was more than 0.3%,they are significantly lower than that of the control. So,increasing the amount of potassium humic acid can increase the yield and improve N,P and K use efficiency of pakchoi. Dosage of 0.1% can be recommended as the optimal dosage.