Using converter slag as curing stabilizing agents, applying Toxicity Characteristic Leaching Procedure (TCLP) and Fourier transform infrared spectroscopy method of tracking and detection of heavy metals in soil remediation effect of slag powder, and the micro-structure of mixtures (slag powder and heavy metal contaminated soils). It can establish soft sensor mode which is based on Gaussian process regression slag powder on heavy metal contaminated soil remediation effect. by using Gaussian process regression. The results show that the steel slag powder on heavy metals contaminated soil has good repairing effect, 180 d within its restorative effects are maintained over 90%; the repair process is divided into early, middle and late stages, in which the early (1~3 d) repair mode is given priority to with ion exchange high alkaline environment, medium-term (7~42 d) ion exchange and gel setting weaken the enhanced role of the late (56~180 d) form a large number CSH gel, the gel solidification further strengthened; based on Gaussian process regression Steel slag powder on heavy metal contaminated soil remediation effect soft measurement model of the real and predicted values agree well with the data, the absolute error is -1.35 ~-0.48, relative error of -1.448%～-0.497%.