Abstract: In order to solve the problem of orbit transfer of the nano-satellite under the action of micro-thrust of laser micro-thruster, a simplified semi-major axis calculation method for in-plane orbit transfer under the tangential thrust was proposed by using perturbation equation. The influence of the main perturbation factors such as the non-spherical perturbation, the atmospheric perturbation and solar pressure perturbation on the method was analyzed. And the orbital changes of the direct integration of the motion equation under various perturbations were compared with the results from the simplified method. The validity and application conditions of the simplified method was verified. The simulation results show that the orbit maneuverability for nano-satellites can be obtained by simplified calculation method under the tangential thrust of the order of 100N at orbital altitude above 300 km. What is more, for nano-satellite mission design stage, the solar pressure perturbation can be ignored, the atmospheric drag perturbation can be ignored above orbital altitude of 500 km, and the influence characteristics of non-spherical perturbation are similar to those of other satellites.