In order to solve the problem of massive storage of refining slag and improve the strength of solid waste based cementitious materials with large amount of converter slag,the material composition of refining slag,converter slag,blast furnace slag and desulfurization gypsum was optimized in this paper.Firstly,the effects of refining slag,converter slag,blast furnace slag and desulfurization gypsum on the compressive strength of cementitious materials were investigated by orthogonal experiment,and the regression analysis was carried out.Then,a nonlinear regression model was established to optimize the mix proportion of cementitious materials.Finally,the synergistic mechanism of refining slag,converter slag,blast furnace slag and desulfurization gypsum was analyzed by XRD,SEM and TG-DSC.The results show that when the content of converter slag in group Ⅰ is greater than 40%,the compressive strength of the experimental mortar is up to 39 MPa,and there is no significant difference between the predicted value and the experimental value,which verifies the reliability of the nonlinear regression model.The early hydration of the refining slag produced C2AH8,which participated in the synergistic effect of the four element system.The hydration products of all ages were mainly ettringite and C-S-H gel.Synergistic hydration promoted the formation of ettringite and C-S-H gel and enhanced the strength of hardened specimens.The results provide theoretical basis and data support for refining slag utilization.