A robust method of soft variable structure control for fractional-order systems is proposed to achieve a faster response in the presence of model uncertainties and external disturbances. In the proposed system the control signal is continuous and constrained. Our proposed method, through the pole placement algorithm, by designing proper polynomials, and applying a simple optimization routine, leads the system to the robust and desired character within the framework of the stability region. The sufficient condition of stability of the control system is developed based on the stability theory of fractional order linear differential equations, and attributes of the Mittag-Leffler function. Finally, numerical simulations and examples are presented to show the efficiency of the proposed method.