Submersed macrophyte, Potamogeton crispus, was planted in water at depth of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 m in pots, with the aim to study the influence of the water depths on plant adaptability in reproduction, biomass allocation and photosynthetic properties and to elicit the way of energy distribution when they are in different water depths.Results showed that the stem length of P.crispus had an evident correlation with water depth and the appropriate water depth for P.crispus growth was 0.5-2.5 m.At the depth of 0.5 and 1.5 m, Potamogeton crispus turion has the largest clones and highest biomass, and the tallest stem length, respectively.Water depth gradients do not affect the germination of P.crispus turions with germination rates > 70% from deep water 0.5 m to 4 m in the experimental group.The adaptability of P.crispus to different water depths has a strong phenotypic plasticity.Height and biomass vary with different water depths for P.crispus.With the increase of water depth and the decrease of light intensity, P.crispus distributes more energy to the growth of plant height so that it can get more luminous energy, which leads to the gradually reduction of energy to reproductive organs and eventually to a balance of energy distribution.The phe-notypic plasticity can adapt to different light stress and what' s more, it can also change the content of the chlorophyll to further re-spond to different light under stress.Below the depth of 3.0 m, the chlorophyll of P.crispus greatly increased to use of energy effi-ciently, which is illustrated by the comparable light response capacity of the experimental group from 3.0-4.0 m and is still not lower than other groups.