A dc-dc buck converter is an electronic circuit with wide application in power electronics. This converter acts as a nonlinear system then, it is necessary to use a robust controller to control and regulate the output voltage under load changes, circuit elements and other disturbances. In this paper, a new fast terminal sliding mode control (FTSMC) using the property of the terminal attraction as a function of the inverse tangent for buck DC-DC converter is provided. The performance of this new controller is compared with FTSMC common type in terms of output voltage convergence time and input control function structure. The superior property of this controller is low singular effect on the control function. Also, the controller has fast rate of convergence in different situations for output voltage stability in order to use in power electronic device of mechanical motion control systems such as types of robots and electric vehicle are pretty good. Simulation results confirm the proper performance of the new proposed fast terminal sliding mode control method compared to traditional fast terminal sliding mode converter for buck converter.