In this paper, the tracking problem for a desired rotational speed of permanent magnet synchronous motor is considered. There are several features of the proposed problem statement. The uncertainties of the mathematical model of an electric drive, related to changes in the active resistances and inductances of the stator windings and magnetic field weakening eect are introduced into consideration. It is assumed, that control plant is perturbed by unknown bounded load torque, which can not be directly compensated with the help of control inputs. Under these assumptions, the new nonlinear control law for synchronous electric drive based on the step-by-step procedure was developed. For the synthesis of robust control systems, the nominal values parameters of synchronous motor are used. The first step introduces auxiliary variables based on algebraic and dierential equations. Further, due to the choice of real control inputs in the form of discontinuous functions, the relation between the variables is introduced, which leads to the convergence of the tracking errors to zero.