This paper focuses on the shrinkage of concrete, influenced by the different mixing amount of super absorbent polymer—SAP and extra-water. The experiment showed that the SAP-cement-mortar shrinkage is reduced greatly by mixing SAP. Extra-water can improve the function of reducing shrinkage of SAP. When the amount is 20, the shrinkage is lest, account for 57% of blank group’s. The SAP has well effect on the cement mortar shrinkage. Besides, we found that the strength of this group account for 89% of blank group. So the proper amount of SAP and extra-water has poorly influence on the strength of concrete.