The invention belongs to the technical field of sewage treatment and particularly relates to a shiitake mushroom dreg charcoal adsorbent for efficiently removing heavy metal lead and cadmium and a preparation method of the shiitake mushroom dreg charcoal adsorbent. The preparation method comprises the following steps: (1) naturally airing shiitake mushroom dreg, crushing, sieving by virtue of a 20-100-mesh sieve for later use; (2) putting the sieved dreg obtained in the step (1) into a muffle furnace, carrying out high-temperature pyrolysis at 500 DEG C for 2 hours under an anaerobic condition, so as to obtain rough charcoal; and (3) sieving the rough charcoal obtained in the step (2) by virtue of a 100-mesh sieve, so as to obtain high-adsorbability charcoal. The charcoal prepared by virtue of the preparation method has very excellent lead and cadmium removal effects, and the highest removal rates of lead and cadmium in water can reach 99.8% and 99.6%; and the charcoal does not need to be modified, a preparation process is simple, the raw materials are easily available and cheap, and the charcoal has very wide market application prospects.