The invention belongs to the technical field of treating auxiliaries for papermaking wastewater and relates to a compound flocculant for the papermaking wastewater and a preparation method of the compound flocculant. The compound flocculant comprises a polymeric flocculant, modified bentonite and polyacrylamide, wherein the polymeric flocculant is epichlorohydrin and dimethylamine polymer, and the modified bentonite is bentonite acidized by sulfuric acid. The compound flocculant and the preparation method thereof have the advantages that the cheap bentonite is modified and matched with the prepared organic flocculant during use, low comprehensive cost is achieved, and the preparation and application methods are simple are practicable; a small amount of the compound flocculant can evidently lower the TDS, conductivity and COD of the wastewater, and the recycling times of the papermaking wastewater are increased greatly.