In a Co-time Co-frequency Full-duplex (CCFD) system, the ability of Self-interference Cancellation (SIC) is limited if we use negative SIC or radio frequency SIC alone, so the residual Self-Interference Signal (SIS) needs to be further cancelled in digital domain. This paper proposed a digital Self-interference Cancellation algorithm based on spectral estimation, via establishing spectral estimation SIS model, we can analyze the spectrum of the SIS and digital transmitted signal. Then reconstruct the SIS and self-adaption cancellation via the second-order cyclic statistic information of signals. The simulation result shows that the proposed algorithm performance and convergence can effectively improved.