Abstract: For increasing the dosage of paraffin in phase change cementitious composites, the pore forming agent (PFA) was mixed with phase change cementitious composites, in which a part of paraffin was filled into the pores produced by the PFA. The effects of different dosages of paraffin and PFA on the paraffin leakage, mechanical properties and thermal storage performance of phase change cementitious composites were studied. The results show that the dosage of paraffin in the phase change cementitious composites increases from 5.0% to 7.2% and the compressive strength decreases sharply with the content of PFA increasing from 0% to 4%. The optimum dosages of PFA and paraffin are 2% and 5.8%, respectively. The heat storage performance of phase change cementitious composites is enhanced with the increase of paraffin content. In addition, the thermal insulation effect of pores also contributes to the increase of the maximum temperature difference between the outer and inner wall of phase change cementitious composites plate and the decrease of the maximum temperature of the cavity in the measurement system.