This paper described a decoupling algorithm for two signals input and two signals output that is based on non-stationary real signal. Firstly, a model about two non-stationary signals through a linear system outputting two signals was built. According to the model, the system’s decoupling was translated into resolving the system’s decoupling coefficients. Secondly, the requirements of the algorithm were derived which making the algorithm work correctly. The signals being non-stationary and decorrelation must to be emphasized. Thirdly, the source signals are de-mixing from two output signals through the decoupling coefficients. Two coupled signals were decoupled by using the algorithm and the result proves the validity of the algorithm. The algorithm was already applied to a differential testing bench and the decoupling result can satisfy the engineering requirement.