Autogenous shrinkage of cement pastes with different contents of pulverized fuel ashes(PFA) and different watertobinder ratio were measured by a shrinkage test device. Compressive strength of sealed cement paste were also measured. The influence of PFA on the pore structures and micrograph of hydration products were investigated through mercury intrusion porosimetry(MIP) and scanning electron microscopy(SEM), on which the influence mechanism was analyzed. Experimental results demonstrated that autogenous shrinkage of cement pastes decreased with the increased contents of PFA at early age (before 7d), this may be ascribed to inhibition of PFA on the shrinkage. After 7d, however, both autogenous shrinkage, and compressive strength of cement pastes increased. This may be attributed to decrease of pore radius and densification of cement hydration products due to the pozzolanic reaction of fly ash.