To illustrate the contribution of phytoplankton-derived particulate organic matter (PPOM) to endogenous phosphorus (P) cycling and its effects on cyanobacteria blooms, PPOM characteristics, the degradation mechanism, and the growth of P-deficient Microcystis aeruginosa were studied in Lake Taihu. Results showed that PPOM is the most important P pool in the water column during cyanobacteria bloom, accounting for more than 80% of the total P (TP) in the water. During PPOM degradation, the particulate orthophosphate (Ortho-P) is the main species of P release from PPOM in the early degradation stage. The variations of polyphosphate (Poly-P) and phosphodiesters (Diester-P) contents were most significant, which were degraded completely within four days and eight days. Cell density and growth rate of M. aeruginosa using PPOM as P source were similar to those growing on Na2HPO4. The above results show that P in PPOM can be converted into available P by degradation, thus promoting the growth of M. aeruginosa. Therefore, the contribution of P release from PPOM degradation needs to be paid attention to in lake eutrophication control in the future.