Stocking density is widely recognized as a critical husbandry factor in modern intensive aquaculture and inappropriate stocking density is a potential source of chronic stress that may affect the welfare of farmed fish, and increase breeding risk. So far the effect of stocking density on the fish welfare was studied widely. In order to provide reference for selecting suitable stocking density and further researching, this review will focus on the fish welfare indicator such as growth performance, health status, stress response and behavior, to explore how stocking densities affect fish welfare.