The cold resistance, regeneration capacity and salt tolerance of exotic aquatic plant Myriophyllum aquaticum were compared with those of Alternanthera philoxeroides. The results showed that M. aquaticum could grow normally in 4.7-17.4 oC, and could survive in winter, but A. philoxeroides all died; meanwhile, the fragments of M. aquaticum (0.5-5.0 cm) could relive and start to grow in water 1 day later, but A. philoxeroides just could relive and get to grow 3 days later. M. aquaticum also could grow well in the solution with NaCl 0-2 g·L^-1 and survive for 2-4 weeks in the solution with NaCl 4-5 g·L^-1. As M. aquaticum has the strong cold resistance, regeneration capacity and high salt tolerance, there is ecological risk to cultivate M. aquaticum in Ningbo area. So, we must use this plant carefully as a garden plant and control its population to over reproduce and spread.