In order to improve the convergence of a sliding variable in super-twisting algorithm (STA), two linear correction terms are added to the classical STA to form a structure of double closed-loop feedback. The new regulation mechanism can accelerate the sliding variable approaching the sliding surface and simultaneously limit knotty overshoot. A series of simulation results indicate the new modified STA can shorten the settling time of the sliding variable effectively and provide stronger robustness. Moreover, the position tracking test results on DC servo system validate the advantageous performance of the modified STA proposed in this paper.