The invention discloses an immobilized endogenous bacteria biological adsorbent and a preparation method thereof. The immobilized endogenous bacteria biological adsorbent is prepared by combining modified carbon nanotubes with polyvinyl alcohol and sodium alginate immobilized endogenous bacteria. The preparation method comprises the following steps of (1) preparing the modified carbon nanotubes; (2) adding the polyvinyl alcohol, the sodium alginate, and the modified carbon nanotubes into water; performing uniform mixing; preparing an immobilized substrate; (3) after the endogenous bacteria obtained through screening is uniformly stirred with the immobilized substrate, extruding the materials into a calcium chloride solution to perform a cross-linking reaction; obtaining the immobilized endogenous bacteria biological adsorbent. The immobilized endogenous bacteria biological adsorbent has high adsorption performance on Pb<2+>, and has the advantages of great adsorption volume, high repeated utilization rate and the like; the preparation method is simple; the implementation is easy; the control is easy; the cost is low.