The invention discloses fertilizer for Cr (VI) polluted soil remediation and improvement and a preparation method of the fertilizer. The preparation method of the fertilizer comprises the following steps: spraying an EM microbial agent to the surfaces of bagasse and pig manures, then uniformly mixing the bagasse with the pig manures, and composting the mixture to obtain a cured material; adding anOneida silva microbial agent, the EM microbial agent and a desulfovibrio microbial agent into the cured material, uniformly mixing the microbial agents with the cured material, and composting the mixture to obtain a microbial compound; and mixing ferrous sulfate, modified coal ash, ground calcium carbonate and the microbial compound, and granulating the mixture to obtain the fertilizer. The fertilizer can improve the soil structure, improve the soil fertility and remediate and improve a microecological structure of the soil when effectively remediating chromium pollution, finally remetiates and improves the chromium-contaminated soil, and restores the ecological functions.