Social interactions among animals are general phenomena in domestic populations. However, at present, very little is known about the contribution of social effect to the selection efficiency of long-term response. In this study, the selection efficiency of a socially affected trait with different social effect was investigated in a closed nucleus population using stochastic simulation. Some key factors that affect selection efficiency of genetic social effect were also compared. The results showed social effect played an important role in a longer term breeding programme even though social effect had a small effect on the trait of interest. The percentage of expected total response contributed by social effect was up to 15.27 at the end generation under a very low level of social effect (0.3% direct phenotypic variance). The full model with direct and social genetic effect, improved the selection efficiency of social effect and resulted in 4.89, 5.21 and 2.70% more total cumulative selection response than the reduced model, without social effect, under the social effect size of 0.3, 1 and 10% direct phenotypic variance, respectively. The social effect size and group member number showed more effect on the selection efficiency of social effect than other factors.