A modal analysis on vibration of a small wind turbine with single stage line gearbox is studied.A three- dimensional solid model of line gear（LG） transmission system is constructed based on Pro/E software.And by using the modal analysis function of ANSYS,the solid model is imported to ANSYS workspace to establish the finite element model of line gear,and the model of a small wind turbine LG transmission system is analyzed,the natural frequency and the corresponding modes of vibration of the LG assembly are obtained.It provides a reference data for optimization design of a small wind turbine LG transmission system to avoid LG natural frequency of inputting the external excitation and eliminate the resonance,which improve the operation reliability of a small wind turbine.