The utilization of steel slag as resource is very important in the circle economy of metallurgy industry. Because the composition of steel slag is similar to that of the raw materials of ceramic industry, the sintering process of ceramics with steel slag as one of the raw materials was studied, and the ceramic products of high performance were abstained. Based on the study above, the microstructure of slag ceramic and its effect on the performance of ceramic were studied combining the analysis methods of SEM, DTA and XRD and the software FactSage. It's found that the diopside phase was formed in the sintering process, which has significant effects on low temperature sintering and ceramic strength improving. Simulation by software FactSage showed that the diopside phase appears when the content of the steel-slag reaches 25%, while the content of slag is higher there are more diopside phase generation.