Nitrates can easily accumulate in leafy vegetables. Excessive intake of nitrate is a threat to human health. Light is an important influence factor of nitrate accumulation in plants. Using polished rod crowndaisy chrysanthemum as experiment materials, the effect of different light intensity（100%, 70%, 50%,30% natural light） on nitrate accumulation in the process of their growth were studied to provide theoretical basis for safety of the leaf vegetables production. The results showed that when the shading was stronger, accumulation of nitrate was more, but chlorophyll, root activity and nitrate reductase activity was lower. Therefore,in actual production, improve lighting conditions is the key. If necessary, artificial light should be added to reduce the nitrate content of vegetables.