Efficient, cheap and environmental friendly method is necessary to treat heavy-metal wastewater. Microbial adsorption has the advantages of excellent adsorption, low price and environmental friendliness. Microorganisms such as bacteria, fungi and algae can bind heavy metals to their surface of cell walls through electrostatic adsorption, complexation and other processes. However, the adsorption effect of untreated microorganisms is often not satisfied. By physical and chemical modification, immobilization and other methods, the active sites on the microorganisms, can be significantly increased, to improve the removal rate of heavy metals. In this paper, the modification methods of microorganisms, the adsorption ability of modified microbial adsorbents for heavy metals in wastewater and the influencing factors are described. We also discuss the problems of microbial adsorbents, and the future research directions.