The invention discloses a papermaking wastewater flocculating agent and a preparation method of the papermaking wastewater flocculating agent. The papermaking wastewater flocculating agent is prepared from the following raw materials in parts by weight: 12 to 16 parts of polysilicate, 1 to 4 parts of sodium polyacrylate, 10 to 16 parts of aluminum sulfate, 10 to 15 parts of ferric citrate, 8 to 13 parts of calcium hydroxide, 1 to 4 parts of aluminum oxide, 3 to 10 parts of aluminum trichloride, 18 to 25 parts of zeolite, 12 to 18 parts of sodium carboxymethylcellulose, 3 to 8 parts of polymerized molybdenum chloride, 20 to 28 parts of ferric magnesium polysilicate and 40 to 50 parts of water. The preparation method comprises the following steps: putting the polysilicate, the sodium polyacrylate, the aluminum sulfate, the ferric citrate, and the ferric magnesium polysilicate into high-pressure water steam and treating to prepare a mixture A; mixing the calcium hydroxide, the sodium carboxymethylcellulose, the aluminum oxide, the zeolite, polymerized molybdenum chloride and the aluminum trichloride with the water and carrying out ultrasonic treatment to prepare a mixture B; putting the mixture A into the mixture B and treating to obtain the product. The papermaking wastewater flocculating agent provided by the invention has a good coagulation performance and a rapid sedimentation speed; the papermaking wastewater flocculating agent has remarkable effects of removing turbidity, de-coloring, removing oil, dehydrating, removing bacteria, deodorizing, removing algae, removing COD (Chemical Oxygen Demand), BOD (Biochemical Oxygen Demand) and heavy metal ions in the water and the like.