The present invention provides a simplified boost type electric vehicle composite power supply structure and a control method thereof. The simplified boost type electric vehicle composite power supply structure comprises a lithium battery, a super capacitor, MOSFETs, a current-limiting diode, an inductor and a capacitor. When the demand power of an electric vehicle is positive, according to the SOC and the output voltages of the lithium battery and the super capacitor, a composite power supply forms a Boost circuit structure, and the duty ratio of the MOSFET SW1 or SW2 is adjusted; and when the demand power of the electric vehicle is negative, the composite power supply forms a Buck circuit structure, and the duty ratio of the MOSFET SW3 is adjusted, thereby realizing the braking energy recovery of the lithium battery and the super capacitor. According to the present invention, the multimode work of the electric vehicle on a general working condition can be satisfied, and the composite power supply simplifies the structure of a cascaded DC-DC converter, so that the energy consumption of the composite power supply is reduced, the energy conversion efficiency is improved, and a control strategy is simpler.