Carbonation degree was analyzed by means of quantitative X ray diffraction(QXRD) and the electronic probe. The mechanisms of carbonation resistance of phosphoaluminate cement(PALC) pastes were discussed by analyzing the concentration of dissolved Ca2+, ion conductivity, pH of the extracted solution and pore structure of the pastes. The comparisons of the above investigations were conducted with the corresponding pastes of Portland cement(PC) and sulfate aluminate cement(SALC). The results reveal that the loss of the compressive strength of PALC pastes is only 4.5% at the condition of exposure in CO2 of concentration > 90%(by mass) and (50±2)% relative humidity for 45 d compared with exposure for 0 d; while the loss for the corresponding PC and SALC pastes is 13.4% and 29.1% respectively. The carbonation factor α of PALC paste is 0.030, which is 3.08 and 3.94 times lower than that of the corresponding PC (α=0.092) and SALC(α=0.118) pastes.