In order to realize the suitable applications of solar energy in electric vehicle control in the future, and ensure the precision and stability of system transmission characteristics, a 3 000 W highpower MPPT solar power system, based on BUCK chopper circuit, was designed with the principle of discontinuousmode in this paper. Under the circumstance of constantly changing input, the output characteristics of continuousmode and discontinuousmode buck power stage were different from each other. And several tests about output current were carried out when input voltage is different. The results of tests show that according to the test, the stability of output voltage was more stable under discontinuous current mode, and the ripple is less than 5%.The output characteristics of this system meet the technical requirements. As a result, it’s more appropriate to use discontinuousmode to realize the demands of design.