The use of stainless steel slag in alkali-activated cement plays an important role in its resource utilization. Calcium oxide, sodium carbonate and water glass are used as composite activators, and the total alkali equivalent is fixed at 6% (the alkali equivalent of calcium oxide and sodium carbonate is 4%, the alkali equivalent of water glass is 2%). The effect of stainless steel slag content (0%、10%、20%、30% and 40%, the effect of the mass ratio of stainless steel slag to the summation of slag and stainless steel slag) on the compressive strength, flexural strength, splitting tensile strength, strain of interior steel ring, circumferential tensile stress and cracking resistance of alkali-activated slag-stainless steel slag mortar (ASLm) is investigated, and the crack resistance of ASLm was characterized by crack resistance evaluation index A_cr (t). The study found that with the increase of stainless steel slag content from 0% to 40%, the compressive strength, flexural strength, splitting tensile strength, strain of interior steel ring and circumferential tensile stress decrease, while the cracking resistance first increases and then decreases. When the content of stainless steel slag is 30%, the A_cr (t) of ASLm reaches the largest, i.e., the crack resistance is the best.