Montmorillonite is widely used in wastewater treatment due to its unique structure and excellent cation exchange capacity. The adsorption of montmorillonite can be improved by regulating its morphology and structure. In this review, the modification methods, preparation principles and characteristics of montmorillonite were introduced, followed by summarization on several single modification methods and composite modification method, namely acid activation, organically modified, inorganic modification, inorganic-organic modification, biochar modification, and nanomagnetic modification. And the adsorption mechanism of modified montmorillonite for adsorbing heavy metals in water were analyzed. The research progress on the adsorption of heavy metal ions by modified montmorillonite in water were then reviewed. Finally, the optimal choice of adsorbent for adsorbing heavy metal ions by modified montmorillonite were disgussed, and it was pointed out that the synthesis of more environmentally friendly, efficient, and separable and recyclable composite modified montmorillonite adsorption materials is the main research direction in the future, providing useful references for the efficient recovery of heavy metal resources.