The invention discloses a heavy metal contaminated soil remediation agent. The remediation agent is prepared from the following raw materials in parts by weight: 100-200 parts of humic acid, 50-100 parts of biochar, 20-30 parts of composite minerals, 1-5 parts of a compound enzyme preparation and 1-5 parts of a compound microbial agent. The preparation method comprises the following steps:(1)weighing the raw materials;(2)mixing the humic acid, the biochar and the composite minerals, crushing, sieving, adding water, heating, stirring, and cooling to obtain a mixture A for later use;(3)mixing the compound enzyme preparation and the compound microbial agent, adding water and a carbon source, and performing habituated culture to obtain a mixture B; and(4)uniformly mixing the mixture A and themixture B, and drying to obtain the product. According to the remediation agent, mild enzymes and microbial strains are adopted for treating soil, heavy metal and pesticide residues are degraded and adsorbed, and the soil quality condition of the soil is obviously improved.