On the basis of summarizing the mechanism of water resistance destruction of magnesium phosphate cement (MPC) and its repair mortar, the proportion of raw materials, mineral admixtures, additives and curing conditions, such as the effects of water-cement ratio, mass ratio of dead-burned magnesium oxide and phosphate(M/P), particle gradation of raw materials, type and amount of mineral admixture, type of admixture and maintenance temperature and humidity conditions on the water resistance mechanism were reviewed. The urgent problems in the research and application field of MPC water resistance and its repair mortar were analyzed. The technical ways to improve the water resistance and cost of MPC and its repair mortar were proposed, including incorporating mineral dopants, nanoparticle modification, and preferring and upgrading the quality of fine aggregates.