Eutrophication is an important indication of serious water pollution. Phosphorus (P) is a key factor causing eutrophication, because it enhances production in an amplified positive feedback. Submerged macrophytes play an important role in P cycling, especially in shallow lakes. However, most of the submerged macrophyte died in winter.In the decomposition period of submerged macrophytes, the decaying macrophytes may be an internal P source for the lake and considerable quantities of P to the water. So to study the interaction of P among aquatic plants, sediments and water is important. However, the effects of submerged macrophytes on P cycling in lakes during the decomposition period are much less understood. In this study, submerged macrophyte H. Verticillata, V. natans and P. crispus were used as material. Through laboratory simulation experiments to study the relationship between P concentration in water and sediment and environmental factors [pH, redox potential (Eh) and dissolved oxygen(DO)] during the decomposition. The results indicated that submerged macrophyte H. Verticillata and P. crispus increased the concentrations of total P (TP), dissolved total P (DTP), particulate P (PP), dissolved organic P (DOP) and soluble reactive P (SRP) during the decomposition period. V. natans has no significant effect on P concentration, P concentrations maintained in a relative low level (TP, 0.04-0.06 mg/L). The changes of environmental factors have significant effect on P concentration in water. The concentrations of TP in water was significant negative correlated with pH、DO and Eh in the groups of H. Verticillata and P. crispus. However, environmental factors have no significant effect on P concentration in the group V. natans.Sediment P concentrations of total P(TP), HCl extracted P (HCl-P), NaOH extracted P (NaOH-P), inorganic P(IP),organic P(OP) were increased during the experiment course. The concentration of IP mainly caused by NaOH-P.Compared with IP,OP has larger effect on TP, OP has significant positive correlation with OM.