The invention discloses a variable threshold ratio update adaptive filtering algorithm based on the least mean square four order. Firstly, a ratio update least mean square/four order algorithm is provided; a dynamic gain matrix is constructed according to the characteristics of system parameters, which can change the step size of the original algorithm by combining the characteristics of the current parameters; therefore, the tracking performance of the algorithm is improved, and the targets of fast convergence and high steady-state accuracy in the process of sparse system identification are realized; and then, a threshold factor updating mechanism based on the gradient method is provided, which can adaptively adjust the selection of the threshold according to the change of the current system error; therefore, the accuracy of parameter identification can be further improved, and the variable threshold ratio update adaptive filtering algorithm based on the least mean square four order has important research significances and engineering application values.