Water glass(WG) and sodium hydroxide(NH) were selected as alkali activator to prepare alkali activated slag cement stone(AASS), and nitrogen adsorption method was adopted to examine the pore structure of cement stone before and after carbonation. The results show that before carbonation, the specific surface area and cumulative pore volume of AASS activated by water glass are the biggest, and the average pore diameter and the most probable pore diameter of that are the smallest. While in the AASS activated with NaOH, the situation is opposite. Those parameters of Portland cement stone is found between the two. Carbonation reduces the average pore diameter and the most probable pore diameter of all cement stone. However, after carbonation, the specific surface area of AASS increases, and that of Portland cement stone decreases.