The change of particle size of super absorbent polymers （SAP） in different early age extracted pore solutions and the real cement paste environment was observed， then the desorption behavior of SAP in cement paste during early age harden process was analyzed. Results indicate that the change of saturation equilibrium absorption capacity of SAP in different early age extracted pore solutions can not represent the desorption behavior of SAP in the real cement paste environment. Desorption rate of SAP is relatively fast in the early plastic stage after mixing and become prominent during a short period after setting， and then became slowly again at the later harden stage. Water released by SAP in plastic stage reduce the capillary pressure of cement paste， which is benefit to reduce the plastic shrinkage， but consume the ability to inhibit the autogenous shrinkage in harden stage.