Abstract: Self-interference cancellation technology is an important prerequisite for the realization of in-band full-duplex (IBFD) communication. Digital domain self-interference cancellation is the least complex self-interference cancellation technology in IBFD communication systems, and is the last line of defense for self-interference cancellation. However, its elimination ability still needs to be improved, mainly how to deal with the balance between convergence speed and steadystate accuracy, and also have the adaptive ability of mutation channel. In this paper, a new digital self-interference cancellation method for full-duplex systems is proposed, in which the transmit chain employs digital and analog predistortion techniques to eliminate nonlinear distortion of the power amplifier, then an auxiliary receive chain is used to obtain a copy of the transmit chain signal, and the reconstructed self-interfering signal copy is used in the digital domain to eliminate the receive signal residual self-interfering signal and power amplifier residual nonlinear distortion, and cancel part of the receiver phase noise by sharing an oscillator between the auxiliary and normal receiver chains. Simulations show that compared with the existing variable-step-size LMS elimination methods, the proposed method can improve the convergence speed and obtain better elimination ability than the existing variable-step-size LMS methods under the condition of a signal-to-noise ratio of 5 dB.