In the sensorless control of linear oscillating motors (LOM), the sliding mode observer exhibits significant chattering during operation, resulting in low accuracy of the estimated piston stroke signal. This paper proposes an improved double power reaching law (IDPRL) terminal sliding mode observer (IDPT-SMO) to estimate the back-electromotive force signal, which gets the estimated velocity signal and piston stroke signal by improving the linear sliding surface to a second-order non-singular terminal sliding surface (SNTSM), introducing switching functions and terminal attractors in the double power reaching law, and replacing the pure integrator with a second-order generalized integrator (SOGI). This article establishes a sensorless control system model for linear oscillation motor in Matlab/Simulink to simulate and verify the performance of the designed terminal sliding mode observer. Finally, the results show that the proposed method can effectively weaken the chattering problem and improve the control accuracy, while the control effect is good.