The effects of light and nutrient availability, 3 (light) x 3 (nutrient), on growth and N, P and C concentrations of Vallisneria natans were investigated in a microcosm experiment. Growth of V. natans decreased with increased light limitation. Inhibition of increased nutrient loading on the growth of V. natans was observed only in high light treatments, while in medium light treatments there were no significant effects of nutrient enrichment on growth, and the growth of V. natans increased with nutrient enrichment in low light treatments. Low light intensity increased the concentrations of tissue total nitrogen, total phosphor-us, ammonia-N and free amino aeid-N but lowered tissue soluble sugar and starch concentration. The concentrations of total phosphor-us, ammonia-N, free amino acid-N and starch increased with nutrient enrichment. The results indicated that both low light availability and high nutrient availability influenced the growth of V. natans significantly, and that there were interactions between them, showing effects of nutrient enrichment depend on the light availability. Growth inhibition in nutrient enrichments was mainly caused by decreased biomass, but not ammonia toxicity or carbohydrates deficiency. Since the growth of V. natans was severely inhibited by light insufficient in medium and low light treatments, there was no more suppression of nutrient enrichment on growth.