The invention discloses a porous composite capable of adsorbing heavy metals ions and a preparation method and application thereof; the porous composite is prepared by introducing microorganisms to natural polymer material and synthetic polymers as materials; the preparation method includes the steps of 1), preparing a foam substrate; 2), performing microorganism culture and substrate foaming; 3), gelling the foam substrate; 4), purifying the porous material, and drying to remove small molecules hot crosslinked and microorganisms not immobilized to the substrate, lyophilizing after dialysis to obtain the porous composite capable of adsorbing heavy metal ions. The whole preparation process of the natural environment-friendly composite is simple, pollution-free and nontoxic, and the composite is biodegradable; the composite is reusable and biodegradable.