The mortar was steam cured using a constant temperature of 80 ℃ for 12 h steam curing system. After the completion of steam curing， three types of subsequent curing were used： natural curing， water curing and standard curing， while the whole standard cured mortar was set as a comparison group. The early strength development patterns of mortars under different curing regimes were studied， and the pore structure characteristics of mortar were analyzed based on X-ray computed tomography （X-CT） technique. The results show that steam curing at a constant temperature of 80 ℃ for 12 h increases the porosity of the mortar， which eventually leads to a lower 28 d compressive strength of the steam cured mortar than that of the whole standard cured mortar. The compressive strength of the steam cured mortar decreases rapidly with the increase of porosity， and a good linear relationship is shown between them. The water curing and standard curing after steam curing can effectively reduce the porosity of the steam cured mortar and make its 28 d compressive strength higher than that of the mortar naturally cured after steam curing. In addition， there is an obviously negative correlation between the pore volume and sphericity of mortar pores， and the steam curing system will increase the outliers in this distribution law of pore volume-sphericity.