The invention provides a preparation method of an environmentally-friendly cleaning agent. The preparation method comprises the following components in parts by weight: 4-8 parts of potassium carbonate, 3-5 parts of methanol, 3-5 parts of ethanol, 2-4 parts of dimethylbenzene, 1-3 parts of kaolin, 3-9 parts of calcium carbonate and 30-90 parts of water. The preparation method provided by the invention has the benefits that the components are simple, the configuration is convenient, the cost is lower, the cleaning effect is good, no harm exists, cleaning is convenient, the cleaning operation isnot required to be performed repeatedly, a lot of manpower and material resources are saved, and the needs of manufacturers are better met.