To reduce the acceleration time and improve the stability of the scanning speed during the exposure process of the wafer stage, a fifth-order S-curve is proposed. The third derivative of the acceleration is designed as a constant, and the position and speed formulas are calculated based on integration method. Optimization index with minimum time and jerk is proposed, and a modified fifth-order S-curve is designed. Simulation results show that the S-cure can ensure that the wafer stage speeds up to the scanning speed quickly and can stabilize in a short time. The modified S-curve can reduce the step time effectively, and the step movement curve is smooth.