The feasibility of using O3 pre-oxidation and polyaluminum chloride (PAC)-enhanced coagulation for treating slightly polluted algae-containing raw water of the Pearl River was investigated. Results demonstrated that O3 pre-oxidation and PAC-enhanced coagulation have greatly increased the removal of algae, turbidity, and natural organic material compared with PAC coagulation only. Specifically, the greatest removal of chlorophyll-a (chl-a) and TOC attained 97.67% and 32.29%, respectively, at the O3 concentration of 1.0 mg/L and a PAC dose of 6.0 mg/L. 1.0 mg/L O3 pre-oxidation reduces the 60% PAC dose when the residual turbidities reached 0.99 NTU. 2.0mg/L O3 pre-oxidation increased the UV254 removal from 16.97 to 57.28% at a PAC dose of 6.0 mg/L.