Abstract: A device of an improvement on the structure of linear actuator primarily includes a motor body and an output shaft, and at one end of the motor body fixed a gear case in which two sets of planetary gear trains fitted, by which a sun gear of one of the planetary gear trains is disposed at the top of output shaft; according to the above mentioned structure, the mesh teeth number between planetary gear is more to enhance the efficiency of resisting shocks and absorbing vibrates for attaining the intention of reducing cost, decreasing weight, diminishing volume, and promoting better outlook.