Buck converter is commonly used in computer servers and other power supplies. Increasing the switching frequency can reduce the volume of the converter, but the effect of parasitic parameters on the output voltage ripple cannot be ignored. The output voltage ripple of Buck converter is studied in this paper. According to the high frequency equivalent circuit model, the output voltage mathematical expression is solved, the output voltage ripple variations and conditions are obtained, and the conclusion that parasitic parameters affect the value of output voltage ripple is proposed. By designing the experimental prototype of high switching frequency synchronous Buck converter, selecting high bandwidth test equipment and minimum test loop, the experimental measurement of high frequency voltage ripple is actualized, and the correctness of theoretical analysis is verified. This study provides a theoretical basis for the circuit design of Buck converter, and provides relevant experience for high switching frequency experimental measurement.