[Objectives]  To determine the effect of feeding corn or sorghum on the oviposition site preference and fitness of the fall armyworm (Spodoptera frugiperda), and thereby provide information to improve the control of this pest. [Methods]  The oviposition preferences, survival, growth, reproduction, fecundity, food intake and efficiency of conversion of digested food (ECD) of S. frugiperda fed either corn or sorghum at a temperature of 25 were measured and compared, and a life table constructed from the data obtained. [Results]  S. frugiperda preferred to lay eggs on the back of corn leaves. The mean number of egg masses was (3.40±0.55), and the mean number of eggs was (346±72.55). A greater number of egg masses and eggs were laid on corn than on sorghum or other substrates. The survival rate of larvae fed on corn (98.89%) was significantly higher than that of those fed on sorghum (86.78%; P<0.05, one-way ANOVA). The ECD of corn-fed larvae was significantly higher than that of those fed on sorghum (P<0.05, one-way ANOVA) and the total developmental duration of corn-fed larvae was significantly shorter than that of sorghum-fed larvae (P<0.05, one-way ANOVA). Comparison of life table parameters indicates that the net reproductive rate (R₀) of corn-fed larvae was significantly higher than that of sorghum-fed larvae (P<0.05, one-way ANOVA). The average net reproductive rates (R₀) of corn and sorghum-fed larvae were (415.93±69.69) and (372.45±34.70), respectively. [Conclusion]  S. frugiperda can complete its life cycle on either corn or sorghum, but larvae raised on corn had higher fitness. However, because S. frugiperda can also complete its life-cycle on sorghum, and the corn and sorghum growing periods are almost the same, there is a risk of this pest spreading to sorghum from corn crops.