Aiming at the radio frequency(RF) fingerprint identification of the wire less transmitter in low SNR condition, a novel RF fingerprint transform method b ased on nonlinear parameters in power amplifier for wireless transmitters is proposed. Based on nonlinear power amplifier models and wireless channel, Kalman filter is applied to estimate the nonlinear coefficients of the model of amplifier with the prior knowledge of communication frames,and the coefficient vec tors are used as RF fingerprints for the identification of the a ccording transmitters hardware. Theoretical analysis and numerical simulations d emonstrat e that the novel RF fingerprint transform method has the advantage in high accur acy at low signal to noise ratio(SNR). The proposed RF fingerprint transform m ethod c an be used in the physical layer fusion identification of wireless or wire comm unication individuals.