The invention discloses a method for enhancing the non-uniform variation grid width of the light load efficiency of an integrated switch DC-DC converter, a Buck-Boost converter in the invention adopts the design of a CSMC 0.5mu m CMOS process library, whole-circuit integration is realized except for a passive filter, the external filter inductance is 2.2mu H, and the filter capacitance is 1mu F. According to the requirements of input voltage and output voltage, the converter can work in three modes: Buck (voltage reducing), Buck-Boost (voltage reducing and boosting) and Boost (voltage boosting), the range of the input voltage is 2.5V-4.2V, the range of the output voltage is 1.5V-5V, and the working frequency is 5MHz. A non-uniform grid width modulation method is adopted in the whole load current range of 10mA-650mA. When the converter works at high frequency of 5MHz, the efficiencies of medium load and heavy load keep above 90 percent all the time, and the efficiency of light load (10mA) can reach above 80 percent. As the grid width of a switching tube is only changed and a control link of the working efficiency of an extra switching tube is not adopted, negative effects caused by frequency conversion control are eliminated fundamentally.