The invention discloses a parameter identification method of a synchronous generator excitation system, which is used for outputting an optimal solution of a parameter Theta of the synchronous generator excitation system. The parameter identification method comprises the following steps of building an excitation system simulation module M; determining an equivalent standard J; and carrying out disturbance test on the excitation system with a signal X, and acquiring each real response index Y. The parameter identification method also comprises the following steps of determining weight W corresponding to the Y, wherein Sigma W is equal to 1; selecting a value of the parameter Theta, substituting the value of the parameter Theta into the M, carrying out disturbance test on the M with the signal X, and acquiring each real response index Y; calculating an error e between the Y and the Y, and calculating a weight value e of the error e if the error e conforms to the equivalent standard J; and taking the value of the parameter Theta as the optimal solution to be output if the e is the minimum e, wherein the numbers of the Y and the Y are both N, and i is equal to 1, 2 until N. By the parameter identification method, the optimal solution can be found out from a parameter solution cluster of the synchronous generator excitation system, and the identification speed is increased within an acceptable precision range to the great extent.