In order to explore the effect of accelerated carbonation on the mechanical properties， carbonation degree and microstructure of hardened white Portland cement， the contents of Ca（OH）₂ （CH） and CaCO₃ were quantitatively characterized by thermogravimetric analysis （TG）， the microstructure was analyzed by electron scanning electron microscope energy spectrum （SEM-EDS） and the mercury intrusion porosimetry （MIP）. Compared with natural curing samples of the same age， the results show that carbonation curing can significantly enhance the compressive strength of cement paste at all ages. Carbonation for 3， 14， 28 d can increase the compressive strength by 10.7%， 7.3% and 5.8% respectively， and the flexural strength by 17.9%， 16.1% and 14.3% respectively. The content of CH can still be significantly increased for the sample carbonized for 14 d after continuous dry wet cyclic curing for 7 d， and the carbonization degree tended to be stable after 28 d of carbonization. The porosity of carbonized samples is slightly higher than that of natural curing samples， and the average pore diameter is lower. The number of larger pores of 50-200 nm is greatly reduced， while the number of micro pores less than 20 nm is relatively more； the accelerated carbonation reaction under atmospheric pressure occurs directly on the surface of CH crystal produced in cement hydration . The carbonation degree is the highest at the edges and corners of the CH crystal， and the carbonation product coexists with it.