The components and test conditions has great effect on the mechanical properties of mortar. Therefore, the content of concrete reclaimed powder, manganese slag, Na2SO4 and the ratio of water to cement were discussed. The pore structure parameters (pore homogeneity, average pore diameter and dry apparent density) of the mortar were determined by the water absorption kinetics method. The mechanical properties of the mortar after high temperature were also measured. The results show that adding mortar with proper amount of Na2SO4, recycled powder of concrete, manganese slag or reducing the ratio of water to cement can improve the flexural strength of mortar, and the effect was more significant in the early stage and then decreased. Appropriate amount of manganese slag content is conducive to improving the mortar compressive strength and high temperature performance. Na2SO4, concrete reclaimed powder, manganese slag and water-cement ratio all can change the pore size distribution of mortar to a certain extent and refine the pore structure. Therefore, the proper amount of recycled concrete powder, manganese slag, Na2SO4, incorporation or reduce the water-cement ratio is conducive to improve the mortar flexural/compressive strength and high temperature performance, and refine the pore structure of mortar.