Most shallow lakes in China are eutrophic or eutrophicating, which are accompanied by aquatic plant disappear. The most effective method of controlling internal nutrient loading may be to restore the macrophytes especially submerged plants in eutrophic lakes, but this method may not success because epiphytic algae which can be increased by high nutrient inload can decrease photosynthetic available radiation of submerged plants, so it is necessary to research the relationship between periphyton and aquatic plants on different water nutrient levels. In this study, periphyton on leaves of Potamogeton crispus, water nutrient level and plant's decay degree were investigated in five ponds which were dominant with P. crispus community and located in the northeast of Nanjing. DW, TOC, Chl.a content, and algae cell counts of periphyton were measured for expressing periphyton characteristics, Chl.a content of P. crispus leaves were measured to indicate plant's decay degree, TN and TP were measured for discripting the water nutrient level, then correlation among periphyton characteristic, plant's decay degree, and water nutrient level were analyzed. Results show that: i) there is a significant correlation between biomass of epiphytic algae and water nutrient level; ⅱ) there is a certain correlation between biomass of periphyton and plant's decay degree, but correlation trend existed difference between different location, two of them are positive and the other three are negative; ⅲ) biomass of periphyton has a negative correlation with plant's decay degree at locations with higher water pollution degree, on the contrary, when the water pollution degree is low, there is a positive correlation between biomass of periphyton and plant's decay degree. We conclude that high water nutrient level can promote the growth of epiphytic algae, but periphyton increase aquatic plant decay only in the case of waters with higher pollution degree.