Superabundant fat tissues in human body affect body beauty and health. In order to enhance the efficiency of lipolysis, pulsed lasers with high absorption coefficients can be selected. But they can not easily penetrate epidermis and dermis perfectly, the lasers can not irradiate and eliminate fat finally. Based on the fundamental principles of ablative fractional photothermolysis and selective photothermolysis, focused Q-switched mid-infrared laser pulses with wavelength of 2.75 mm are used to ablate epidermis and dermis, microscopic path is formed, which can help focused Q-switched infrared laser pulses with wavelength of 2.3 mm transmit through the path without energy loss to eliminate fat tissues selectively. The treatment products can be discharged through metabolism. Microscopic treatment zones affected by adjacent tissues heal soon. The harmonious compromise between safety and validity for lipolysis treatment can be realized. The research will offer a new method for dermatologic surgery treatment.