Under the premise of ensuring the controllable setting time, improving the early strength of potassium magnesium phosphate cement is the key to its engineering application. In this study, borax and sucrose were used as retarding components to regulate the hydration and hardening process of potassium magnesium phosphate cement. The results show that compared with the single-doped borax and single-doped sucrose groups with the same setting time, the second exothermic peak of potassium magnesium phosphate cement mixed with the two (borax and sucrose account for 1.5% and 6.0% of the mass of MgO, respectively) is significantly delayed, but the heat release rate and total heat release increase. The amount of hydration product MgKPO4·6H2O is more, the 3 h strength increases by 104.1%, and the later strength is equivalent to that of the single-doped borax group.