The invention discloses a passivating agent for governing heavy metal contaminated soil and a preparation and use method of the passivating agent. The passivating agent comprises, in weight percent, 30%-50% of clay minerals, 10%-20% of phosphate, 10%-15% of reducing agents, 10%-15% of sulfide and 15%-20% of alkaline substances. The preparation method includes a step: mixing the clay minerals, the phosphate, the reducing agents, the sulfide and the alkaline substances to mix to obtain the passivating agent. The use method includes the steps: firstly, crushing the heavy metal contaminated soil; secondly, adding the passivating agent into the crushed heavy metal contaminated soil; thirdly, adding water into the crushed heavy metal contaminated soil added the passivating agent to uniformly mix, maintaining the uniformly mixed soil on site, and enabling the passivating agent and heavy metal in the soil to sufficiently react. The passivating agent can effectively meet the urgent requirements of current Chinese heavy metal contaminated soil for high stability, no secondary pollution, durable and stable effect and low cost.