Abstract: Epiphyte is commonly involved in the material transformation of water ecological system, and plays an important role in the shift between macrophyte-dominated and algal-dominated lake ecosystems. In order to study the inhibition effect of epiphyte on photosynthesis rate of the plant and the relationship between epiphyte biomass (w) and nitrogen and phosphorus level, the biomass and net primary production of epiphyte attached on submerged macrophyte Potamogeton crispus collected from 8sampling were studied in Baiyangdian Lake in May of 2012. The results showed that the biomass, the chlorophyll-a (Chla) content and primary production of epiphyte were positively associated with concentrations of nitrogen and phosphorus. The maximum values were found at the site of Wangjiazhai, where concentrations of nitrogen and phosphorus were 6.074mg/L(TN) and 0.161mg/L(TP) respectively, and the biomass, Chla content and primary production of epiphyte were 0.073-0.384,0.019-0.112 mg/g and 0.007-0.154mg/(g·h), respectively. The photosynthesis efficiency of P. crispus was significantly inhibited by the epiphyte, and the maximum inhibition rate was up to 72% at Wangjiazhai, followed by Nanliuzhuang and Duancun with inhibition rates of 64% and 55% respectively. However, the photosynthesis rate of P. crispus only decreased by 11% with a low nutritional level at Guangdian. The shading effect of epiphyte might affect the growth of P. crispus. It could be concluded that epiphytic community is an important component for aquatic ecosystems and the primary production of epiphyte was significantly affected by concentrations of nitrogen and phosphorus. This study would provide a basic information on the recession of submerged vegetation in the eutrophicated water.