Effect of starch on the granulation of sludge which is rich in PAOs was comparably studied with two reactors:without starch addition(1#), and with starch addition(2#). The granulation of the sludge granulars within the reactors, as well as the removal efficiency of COD, TP was investigated via the using of scanning electron microscopy, ultraviolet spectrophotometer and particle instrument. The granulation was fulfilled in 24 days during the operation of the 2# reactor, and was 25% shorter than that of 1#. A higher content of protein observed from the sludge EPS in the 2# reactor suggested that the existence of starch led to a higher production of amylase, and consequently to a fast granulation. In comparing with 1#, 2# exhibited a higher biomass concentration and need more O₂ in aerobic unit, thus resulted in a denser granule sludge structure, which maintain a stable operation of the reactor. The additive of starch as 30% of the COD in the 2# system showed no negative effect on the bulk removal of phosphorus, with an average TP and COD removal efficiency of 95% and 90% respectively. The efficiency system changed insignificantly even if the starch additive was stopped.