Solidiﬁcation / stabilization (S/S) is a popular method for treating solid wastes containing heavy metals. In recent years, it shows positive results of magnesium potassium phosphate cement as stabilizing agent. In the work, the influence of heavy metal Cu、Zn and Pb on magnesium phosphate cement and the leaching behavior of magnesium phosphate cement were studied. Two proportions of cements were employed with hard burned magnesia and potassium phosphate. The hydration products were analyzed by XRD showing that: Cu、Zn and Pb would not take on obvious effect during magnesium phosphate cement hydration process. Leaching toxicity tests showed that: Cu、Zn and Pb were immobilized within cement hydration products through physical fixation, adsorption mechanisms, and the results were far lower than that of the National Standard in China.