Digital-domain self-interference cancellation (SIC) technology effectively addresses the SI issue by reconstructing the SI signal, and is one of the key techniques for in-band full-duplex (IBFD) communication systems. Due to the high computational complexity of the traditional Recursive Least Squares (RLS) algorithm in SIC, its real-time engineering application capability is limited. To overcome this limitation, this paper presents an RLS-SIC algorithm based on dichotomous coordinate descent(DCD). The method transforms the original normal equations of the RLS algorithm into auxiliary normal equations, and by combining a bisection search strategy, it significantly reduces the computational complexity while maintaining optimal convergence performance. Simulation results demonstrate that the proposed algorithm not only achieves a significant reduction in computational complexity but also retains SIC performance, thus enhancing the practical application value of full-duplex(FD) communication systems.