A new kind of power function exponential reaching law was designed based on exponential reaching law.The intelligence features of the exponential function were used to associate the speed of the trajectory with the distance of velocity to the sliding mode surface,and adaptive adjustment was implemented.The reaching law could suppress the chattering of the exponential reaching law when it crossing through a sliding mode surface.The power function exponential reaching law was applied to the Buck converter.A specific Matlab/Simulink module was presented,and the simulation verified the effectiveness of this method.