To stabilize the flowability of cement-based materials mixed with super absorbent polymer （SAP），the porous poly（acrylic acid/acrylamide） SAP was prepared by inverse suspension polymerization. The microscopic morphology and the molecular structure of the SAP were observed by scanning electron microscope（SEM）， and Fourier infrared spectroscopy（FTIR）， respectively. And the liquid absorbing properties of the SAP were determined by using tea bag method. In addition， the effect of non-porous and porous SAP on the fluidity loss of cement paste was studied through fluidity tests. The results show that the porous SAP with micro porous structure can effectively promote its water absorption rate， and it takes only 1 min to reach the water absorption balance. When the initial fluidity is maintained by additional water， the addition of porous SAP has the least effect on the fluidity loss of the paste over time.