Alkali slag recycled concrete is a new type of concrete prepared by replacing cement with alkali excited cementing material and natural stones with recycled aggregate, which can effectively reduce the amount of Portland cement and improve the utilization rate of waste concrete. However, there has been no relevant research on its mechanical properties. In this paper, the effects of steel fiber substitution rate and recycled aggregate substitution rate on compressive properties, splitting tensile properties and flexural properties of alkali slag recycled concrete are studied. The results show that: With the increase of recycled aggregate, the cube strength fcu, splitting tensile strength ft and flexural strength fw of recycled alkali slag concrete all decrease, and the reduction range is 30%, 10% and 15% respectively when the substitution rate of recycled coarse aggregate is 100%. The cube strength and splitting tensile strength of alkali-slag recycled coarse aggregate concrete with increase first and then decrease with the increase of steel fiber volume substitution rate. When the steel fiber volume substitution rate is 0.6%, the compressive strength and flexural strength reach the maximum value. The flexural strength of alkali slag recycled concrete increases with the increase of steel fiber volume substitution rate.