A nonsingular terminal sliding mode(NTSM) control scheme with the disturbance observer is presented for second order uncertain SISO nonlinear systems. An improved NTSM function is proposed to improve the convergence rate of reaching the sliding surface, and it is proved that the reaching time of the proposed method is smaller than the traditional NTSM. To estimate the chattering phenomenon caused by disturbance influence variable in the system, a linear disturbance observer is employed to reduce the switching term gain of sliding mode control, and a Sigmoid function is used to replace the traditional sign function. Simulation results show the effectiveness and correctness of these conclusions.