An additive effect is the main genetic determinant of the phenotypic value of a quantitative trait, but it is a direct genetic effect (DGE) of the trait itself, ignoring the genetic influence of social interaction among individuals in the same group. The expression of genes of an individual has an influence on the phenotypic values of others in the same group, which is an indirect genetic effect (IGE). IGE is generated by social interaction among individuals in the group. IGE has been widely reported in animals and plants. For aquatic animals, IGE has been determined in Nile tilapia, Atlantic cod, and the Pacific white shrimp. The Chinese shrimp () is one of the most representative aquaculture species in China. In , cannibalism and frequent attacks are common phenomena. Attacks among individuals under environmental stress and the fight for food may affect the growth of shrimps. In order to study the indirect genetic effects of body weight in under restrictive feeding conditions, 103 families of the eleventh generation of the breeding population were tested using a multi-family by multi-group design. They were reared for about three months with limited feed and harvest body weight was measured for each individual. Genetic parameters of harvest body weight were estimated using an extended animal model, including IGE. The results showed that the IGE of body weight was significant, with a contribution to the total genetic variance reaching up to 75.03%. There was a negative covariance (-2.1900) between DGE and IGE. Based on the model with IGE, the ratio of total genetic variance to phenotypic variance was 0.524±0.212, which was less than the traditional estimate of heritability (0.616±0.074). In addition, there was a negative genetic correlation between the direct and indirect genetic effects (-0.495), implying that the existence of competitive effects may be detrimental to selective responses. This study demonstrated strong social interaction (competition among individuals) exists in a population of under restrictive feeding conditions, which had a heritable effect on body weight. Considering that the indirect genetic effect under the competitive environment has a greater negative impact on selection, it is inadvisable to conduct breeding programs under a competitive environment.