To meet the needs of different working conditions, a double-stator multi-motors was designed. Double-stator single-acting multi-motors was one of double-stator multi-motors. In order to realize the performance of motor, the influence of torque pulsation by different number of slider was studied based on the analysis of the theoretical displacement and theoretical torque of double-stator single-acting multi-motors. Through the analysis, mathematical expressions of the motor torque and the number of sliders were obtained. Meanwhile, the results show that the lag angle can influence torque pulsation when outer motor and inner motor work at the same time and differential connection. It turns out that the uniformity of angular velocity is smaller when the number of alien slider is odd, while the amplitude of angular velocity is a little larger than the motor whose number of sliders is even. This research work lays a theoretical foundation for the design of double-stator single-acting multi-motors.