The invention discloses a comprehensive washing remediation method for heavy metal contaminated soil. The comprehensive washing remediation method comprises the following steps: ploughing and smashing soil, applying acid and alkaline washing agent solid materials, then drawing water when ploughing, washing and dissolving heavy metal out of the soil, and transferring the heavy metal into washing water; guiding the washing water into a sedimentation tank, adding a coagulant, and removing the heavy metal in the washing water through coagulation and sedimentation; draining the washing water into a microorganism and biochar purifying tank, utilizing biochar bags to absorb the heavy metal, and at the same time, enriching the heavy metal through microorganisms on biochar surfaces; and collecting used biochar bags, adding a dilute acid solution into the biochar bags, stirring, and separating the heavy metal absorbed to the biochar surfaces. The invention further discloses a corresponding comprehensive washing remediation system. The technical scheme of the invention greatly increases the absorption rate of the heavy metal, avoids heavy metal secondary pollution, is simple in technical process, is high in automation degree and is low in cost.