Abstract: In this study, a novel approach to the super-twisting sliding mode control of dynamic uncertain systems is proposed. The idea behind this control scheme is to utilize a time varying slope in the sliding surface function using a simple single input-single output fuzzy logic inference system so that the sliding surface is rotated in such a direction that the tracking performance of the system under control is improved. Computer simulations are performed on a system with parameter uncertainties and external disturbances. The results are compared with a conventional super twisting sliding mode controller with a fixed sliding surface. The results have shown the improved performance of the proposed approach in terms of a decrease in the reaching and settling times and robustness to disturbances and parameter uncertainties as compared to the conventional super-twisting sliding mode controller with a fixed sliding surface.