The effect of the content of blast furnace slag on the workability and mechanical properties of steel fiber reinforced self-compacting concrete （SFRSCC） was studied. The strengthening effect of steel fiber and blast furnace slag on the concrete matrix was explained in a view of microstructure level. The results show that substituting 10% cement with blast furnace slag can effectively improve the workability of fresh concrete， while increasing fiber volume fraction can obviously weaken the workability of self-compacting concrete. The synergistic effect of blast furnace slag and steel fiber can significantly improve the compressive strength， splitting tensile strength and flexural strength of hardened concrete. Replacing cement with blast furnace slag is efficient to generate a denser microstructure.