An outdoor experiment was conducted to examine effects of damage on the growth of submerged macrophyte Elodea nuttallii from May to July in 2006. There were three damage treatments: growing tips removed, 50% defoliation and 50% defoliation and growing tips removed. Results showed that three damage treatments affected plant relative growth rate, length of main shoot and lateral shoots, and content of dry mass, nitrogen and phosphorus of plant tissue. Compared with undamaged plant, plant relative growth rate was only 62.8% for 50% defoliation treatment and 74.4% for 50% defoliation and growing tips removed treatment. The main shoot growth of plant in removed growing tips treatment and 50% defoliation and growing tips removed treatment almost stopped, but lateral shoots grew significantly. This study suggests that plant fragments may be responsible for the increasing standing biomass of E. nuttallii in East Taihu Lake in recent years.