The invention relates to a dynamic system static gain estimation method based on historical data slope response. The method comprises: firstly, analyzing historical data, and dividing an input time sequence and an output time sequence into short data segments by adopting a piecewise linear representation method; secondly, finding out a slope response in which input and output are linear at the same time and amplitude change is large, and determining a threshold value with large amplitude change according to a relation between the amplitude change and a determination coefficient; and finally, solving a plurality of linear equations with relatively large slope response amplitude change to obtain the estimated static gain. The effectiveness of the method can be visually verified, and the problem that static gain estimation is difficult to verify by using a system identification method is solved. Therefore, the situation that the deviation between the estimated static gain and the actual gain cannot be judged is avoided.