The invention discloses a slag-forming agent for fusion casting of environment-friendly zinc and a zinc alloy, which belongs to the technical field of fusion casting process of the zinc and the zinc alloys. The slag-forming agent comprises the following components by weight percent: 3%-10% of AlCl3.6H2O, 3%-10% of pulverized coal, 2%-5% of Na2HPO4.12H2O, 2%-5% of ZnCl2, 50%-65% of fluorspar powder, 10%-15% of NaCl and 8%-10% of KCl. The slag-forming agent does not contain ammonium salt, nitrate, C6Cl6, CCl4 and other substances which can cause toxicity and heavy pollution and are commonly used in the traditional slag-forming agent. The application of the slag-forming agent in the fusion casting slag-forming treatment process of the zinc and the zinc alloy can significantly reduce the quantity of slag, emit less smoke dust during the slag-forming process, further greatly improve the working environment and significantly reduce the environmental pollution.