Based on the life-table parameters and the release effects of Amblyseius cucumeris (Oudemans) under laboratory and field conditions, the control efficiency of A. cucumeris (Oudemans) on Panonychus ulmi (Koch) was evaluated. When feeding on P. ulmi, A. cucumeris could complete its development period and lay eggs with one generation time of 9.54 d at (25 +/- 1) degrees C. The egg-laying period (24.85 d) and lifespan (38.52 d) of female A. cucumeris were longer than their preys (15.93 d and 34.79 d, respectively), but the average amount of eggs laid by female A. cucumeris was 36.70, being 43.9% less than that of P. ulmi. The net reproductive rate (R0) and intrinsic rate of natural increase (r(m)) of P. ulmi were 103.9% and 13.2% higher than those of A. cucumeris, respectively. No matter what the good-harm ratios was 1 : 30 or 1 : 150, the control efficiency of A. cucumeris after its 20-day release under laboratory condition could be over 95%, and the efficiency after 60-day release under field condition could be 91.73%, being 23.77% higher than that when sprayed with pesticide, suggesting that A. cucumeris was a good biological agent to control the population growth of P. ulmi. When the P. ulmi population density was less than 2 per leaf, releasing A. cucumeris in the orchard could effectively control the population increase of P. ulmi.