The actuality and faults of actuator fault diagnosis was analyzed, the components transfer function of electric actuator and the whole transfer function of electronic actuator were set up. The LAV algorithm was used to estimate the transfer function and the parameter of the function. By comparing the normal value and estimated value, a conclusion reviewing exceeding faults or damage faults could be drawed. The relationship between the transfer function parameters and the parts of actuator, where being of the fault. The algorithm provided an effective method for fault diagnosis.