[Objectives]  To study the effect of different diets on the digestive efficiency, nutritional content, larval development and digestive enzyme activity of Cnaphalocrocis medialis. [Methods]  The digestive efficiency, nutritional content, developmental duration and digestive enzyme activity of C. medialis larvae reared on either an artificial diet, rice leaves or maize leaves, was measured and compared. [Results]  C. medialis was able to complete its life cycle on all three diets but had different developmental durations and pupal weights on each diet. C. medialis reared on rice leaves had the shortest developmental duration and the heaviest pupae. There was, however, no significant difference in the fecundity, oviposition period or adult longevity, of C. medialis reared on different diets. C. medialis reared on rice leaves were significantly more efficient at converting digested food (ECD) than those reared on maize leaves or the artificial diet. The approximate digestibility (AD) of larvae reared on the artificial diet was 52.32%, significantly higher than that of larvae reared on rice or maize leaves. C. medialis larvae reared on the artificial diet had higher soluble protein and sugar content than that of those reared on rice or maize, but lower fat content. Protease, amylase and lipase activity in the midguts of larvae fed on the artificial diet was significantly higher than that of larvae fed on rice or maize. [Conclusion]  Diet affected the development and nutritional composition of C. medialis. This species appears able to ensure adequate nutritional uptake on different diets by adjusting its feeding behavior and the activity of midgut digestive enzymes.