The migratory fall armyworm, Spodoptera frugiperda (Smith), has become an important agricultural pest worldwide. In this study, a comparative analysis of the cannibalistic behavior of S. frugiperda larvae in different instar stages was carried out. The predation function of S. frugiperda and the effects of cannibalism on the development of S. frugiperda were assessed based on the Holling functional model and two-sex life tables, respectively. The functional response results reflected that the 3rd, 4th, 5th and 6th instar larvae of S. frugiperda exhibited theoretical maximum predation values of 82.89, 83.39, 110.52 and 111.2, respectively. According to observations of the development of S. frugiperda under three treatments, S. frugiperda completed its life cycle in the control and cannibal groups but not in the only cannibal group. The larval and pupal developmental duration in the control group and the cannibal group were significantly different. S. frugiperda in the cannibal group had the shortest adult period (5.82 d) and the lightest pupal weight (0.1387 g); the survival rate in the cannibal group was lower than that in the control group. Significant differences were observed in the mean fecundity of females, with the largest number of eggs (1075.06 eggs) laid by S. frugiperda in the control group. S. frugiperda in the control group had the highest intrinsic rate of increase (r), net reproductive rate (R0 ) and finite rate of increase (λ). Overall, cannibalism is not conducive to the growth and development of S. frugiperda.