The invention relates to a dynamic soft measurement method and system based on slow characteristic regression. The method includes the steps of reading a slow characteristic model and a linear regression model, reading in online measurement values of operating variables, inputting the online measurement values into the slow characteristic model, and obtaining an online real-time estimated value of a slow characteristic vector s(t); inputting a vector s<1:M>(t) composed of the first M slow characteristics into the linear regression model, and obtaining an instant estimated value (please see the specification) of the leading variable y(t) difficult to measure; writing in and displaying the estimated value (please see the specification) of the y(t). By means of the dynamic soft measurement method and system in the technical scheme, the dynamic characteristics of a process can be effectively mined, the estimation accuracy is higher, the more excellent control performance is achieved when closed-loop feedback control is implemented, the prediction accuracy of a current model can be visually and effectively judged according to the slow change degrees of the hidden characteristics when field implementation is carried out, and the information in large-scale process data can be effectively used.