The invention belongs to a washing agent, concretely relates to the washing agent specially used for female underpants with the characteristics of stable product performance, long storage life, strong multienzyme decomposition capability on organic matter, good effect for cleaning the contaminants on the female underpants, bacteriostasis and disinfection, and its preparation method. The washing agent comprises the following raw materials by weight part: 50-118 parts of surfactant, 10-34 parts of propylene glycol, 10-34 parts of triethanolamine, 1 part of ethylparaben, 12-40 parts of enzyme stabilizing agent, 1-26 parts of sodium hydrosulphite, 0.04-2 parts of calcium chloride, 2-25 parts of sodium citrate, 4-20 parts of citric acid, 2-15 parts of protease, 3-10 parts of biological enzyme used for compound and 11-238 parts of deionized water; has the advantages of good hard water resistance, nontoxicity and innocuousness, flexibility, antistatic property and shrink resistance, and is capable of obviously increasing the softness of the washed cotton fabric, so that the fabric is soft and the color is white, the washing agent has inhibition effects for a plurality of bacteria and mildew, and the cleanness and sanitation of the underpants can be ensured.