A composite coagulant, polymeric aluminum ferric chloride-poly-epichlorohydrin-ethylenediamine (PAFC-EPI-ETA), was synthesized and then used for the treatment of synthetic reactive brilliant red (RBR) dyeing wastewater. Effects of (Fe + Al) to EPI-ETA mass ratio (P) on the color removal and zeta potential were investigated under different coagulant dosages and initial pHs. Experimental results indicate that the removal of reactive dye and the charge neutralization ability of composite coagulant were improved by increasing the content of organic EPI-ETA. PAFC-EPI-ETA with P = 1 achieved the best color removal percentage and strongest charge neutralization ability. Decolorization efficiency using PAFC-EPI-ETA was quite effecient with pH range of 6.0–7.5 for RBR dye removal. Characteristics of the formed floc were investigated with the dosage of PAFC-EPI-ETA under different P values. The low (Fe + Al) to EPI-ETA mass ratio contributed to the formation of flocs with high growth rate, large size and large size variation.