The present invention relates to the parameter optimum estimate of the convertor, specifically a device and a method for estimating the linear and non-linear parameter of the model (11). The model relates to a convertor (1) which converts the input signal x(t) into the output signal y(t), such as the electric signal, the mechanical signal and the acoustic signal, wherein the convertor mainly is an actuator (loudhailer) and a sensor (microphone), also can be the electrical system for storing, transmitting and converting the signals. The model describes the internal state of the convertor and the transmitting character between the input and the output of the small and large signal domain, and the information is the basis of the measuring application, the quality evaluate and the failure diagnose and the driving control convertor. The aim of the invention is to realize the linear and non-linear parameter pl and pn of the model without system error (warp), which is realize through estimating the transmitting system (55) of the linear and non-linear parameter using different functions.