A composite flocculant, polymeric phosphate-aluminum ferric chloride (PPAFC), in this study was synthesized through hydrolytic polymerization of PAC, FeCl3.6H2O and Na2HPO4, which was used to coagulate humic acid. Scanning Electron Microscope (SEM) was employed to characterize the PPAFC. Humic acid being an important component of the aquatic environment has posed a potential threat to human health thus receiving wide attention. Therefore, the purpose of this study was also focused on removing humic acid from water by the coagulation-flocculation process, especially with the PPAFC. Since the flocculation performance was often determined both by the added flocculants and the operational parameters such as rapidly mixing time, rapidly mixing speed and pH, the response surface methodology (RSM) with humic acid removal efficiency as response value, was herein used to analyze the mutual effects of these parameters so that a better flocculation efficiency could be obtained under an optimum conditions. As a result, the RSM model was significant and for flocculation at a rapidly mixing time, pH and rapidly mixing speed of 2 min, 7.07 and 350 rpm, respectively, the humic acid removal efficiency was 94.28%.