Shrinkage compensating concrete specimens were prepared by adding waste steel slag. Experiment on compressive strength, elastic modulus and Poissons ratios of concrete prism were carried out to analyze the effect of water cement ratio on the failure mode, compressive strength, deformation and stress strain relationship. Test results show that the failure mode of shrinkage compensating steel slag concrete is similar to that of ordinary concrete, the cracking time of shrinkage compensating steel slag concrete is later, the crack growth rate is faster, and the peak strain is smaller. With the decrement of water cement ratio, the bearing capacity of the specimens increases gradually, and the elastic modulus increases at first and then decreases. The deformation, strain and elastic modulus of the specimens are all less than that of ordinary concrete, and Poissons ratio is 23 times of ordinary concrete. Due to the less internal defects and voids of shrinkage compensating steel slag concrete, the linear phase of the stress strain curve is longer, and the bend point of the curve is not obvious. Based on the experimental study of shrinkage compensating steel slag concrete, the calculating formula of the peak stress, peak strain, elastic modulus and Poissons ratio of the shrinkage compensating steel slag concrete is proposed, and then the stress strain model is established. The calculating results of the model are in good agreement with the experimental results.