Abstract: The early cracking in concrete is one of the hot spots of current researches at home and abroad. In this study, in order to explore the influence of the pre-soaked porous steel slag on the early crack resistance of concrete, we mixed the pre-soaked porous steel slag into concrete, replaced part of the coarse aggregate amount and used the knife-edge method to study the early crack resistance of concrete. The test content is mainly divided into two parts, the strength tests and the early crack resistance tests. The analysis results show that 7 d and 28 d compressive strengths of the steel slag concrete are superior to the control group, and only judging by the compressive strength, there is the optimal dosage of the porous steel slag in concrete. After adding the pre-absorbent porous slag to concrete, it causes a delay in the initial cracking of concrete, the maximum crack width and total crack area on per unit area are significantly reduced, and the early cracking resistance of concrete is enhanced significantly. From the point of view of internal curing, analysis results show that the porous steel slag can improve the internal relative humidity of concrete, thus inhibiting the shrinkage of concrete at the early age, and be favorable for the improvement of the early cracking resistance of concrete.