Abstract: In order to explicit the control effect of natural enemies on soybean aphid, the predatory functions of three dominant natural enemies (Harmonia axyridis, Propylaea japonica and Chrysoperla nipponensis) against soybean aphids were investigated in fields in Harbin 2012—2013. Using four factors quadratic regression general rotational combination design and its equation, the relationship between natural enemies and soybean aphids was analyzed. The factors determining soybean aphid population size were ranked as initial soybean aphid number> H. axyridi number> P. japonica number> C. nipponensis number. The optimized combination of natural enemies for soybean aphid control was: adults of H. axyridis (6), P. japonica (1) and C. nipponensis (4) for 100 aphids on two soybean plants, which resulted in 84.60% combined control of aphids; and combination of three larvae of each of the three predators achieved aphid control of 98.89%. When aphid infestation was increased above 100 on the two soybean plants, combination of 6 H. axyridis and 4 P. japonica adults achieved aphid control of 42.33%—52.17%, and combination of 4 larvae of each of the three predators caused aphid mortality of 33.68%—73.17%. The results indicate that natural enemies are effective for control of soybean aphids.