Abstract: To detect the effects of size class,population density and food availability on cannibalism,newborns of larval salamanders (Hynobius amjiensis) were basin-raised in combinations of the ecological factors.Compared with the results of Fu et al (2003),this study evaluated the effect of group size structure on patterns of intra-specific cannibalism.The results showed that:1)Percent of larvae eaten were significantly influenced by size class,density and food availability.Smaller individuals were susceptible to attack by larger individuals.The highest cannibalism of three size-class larvae appeared in the combination of low-density and high-food availability.2)Group size structure significantly affected intra-specific cannibalism.Overall levels of larvae bitten were lower in groups of different-size individuals than in groups of similar-size individuals,but those of larvae eaten were higher in the formers than in the latters.These supported the theoretical prediction that body size determined the cannibalism of a population.