The invention discloses a heavy metal wastewater treatment agent and a preparation method of the heavy metal wastewater treatment agent. The heavy metal wastewater treatment agent is prepared from the following raw materials in parts by weight: 3 to 8 parts of polyacrylamide, 15 to 22 parts of phosphorus ferric polychloride, 12 to 18 parts of gypsum, 20 to 28 parts of zeolite, 10 to 15 parts of sodium lignin sulfonate, 6 to 10 parts of polymerized ferric phosphate, 50 to 58 parts of water, 3 to 8 parts of calcium oxide, 12 to 18 parts of aluminum hydroxide, 3 to 8 parts of calcium chloride, 5 to 10 parts of active carbon, 12 to 15 parts of aluminum potassium sulfate and 5 to 8 parts of diatomite. The heavy metal wastewater treatment agent is prepared by treating the polyacrylamide, the phosphorus ferric polychloride, the polymerized ferric phosphate, the calcium chlorid, the sodium lignin sulfonate and the zeolite by high-pressure water steam to prepare a mixture A, mixing the gypsum, the calcium oxide, the aluminum hydroxide, the active carbon, the aluminum potassium sulfate, the diatomite and the water, and carrying out ultrasonic treatment to obtain a mixture B, and putting the mixture A into the mixture B and treating. The heavy metal wastewater treatment agent disclosed by the invention has a chelating effect on heavy metal, has the advantages of short precipitation time, good effect, low cost and complete treatment, and can be widely applied to the field of heavy metal wastewater treatment.