The invention relates to the technical field of fabrics, in particular to a method for preparing a fabric antibacterial finishing liquid. The method includes the steps of weighing heartleaf houttuyniaherb, astragaloside, indigowoad root, myristic acid, allicin, sweet potato starch, wheat germ oil, ethanol, potassium sorbate, lignin, pomegranate peel, prunella vulgaris, wormwood and caulis clematidis armandii. The remaining raw materials other than the ethanol are mixed evenly to obtain processed powder; the processed powder is placed in a closed container, water vapor is led in, the temperature is maintained at 180 DEG C, the pressure is 0.2 MPa, the temperature and the pressure are maintained for 2 h, then the processed powder is taken out and dried at a high temperature of 260 DEG C, and the moisture content of the processed powder is 4%; and the processed powder is added into the ethanol to be mixed evenly to obtain the antibacterial finishing liquid. The preparation process is simple, it can be fully ensured that effective ingredients of the antibacterial finishing liquid are not lost, and the antibacterial finishing liquid can greatly improve the antibacterial performance ofa fabric, and at the same time the breathability of the fabric is not affected.