The invention relates to a medical ultrasonic coupling agent with a sterilizing function and a preparation method thereof. The ultrasonic coupling agent is prepared from the following effective ingredients: 4-chloro-3,5-dimethylphenol, an acrylamide dimethyl ammonium taurine/vinylpyrrolidone copolymer, polyethylene glycol, a skin-care agent and purified water. The medical ultrasonic coupling agentinvolved in the invention keeps characters and a coupling function of a traditional medical ultrasonic coupling agent; and the disinfectant 4-chloro-3,5-dimethylphenol being harmless to a human bodyand the environment and non-corrosive to a silicon rubber product is selected and prepared into the transparent gelatinous medical ultrasonic coupling agent with the sterilizing and disinfecting function.