Analysis of Cu2+ adsorption on cell surface of a Gram-negative bacterium P. putida 5-x was carried out. Isolated cell envelopes possess fivefold more Cu2+ adsorption capacity than that of the fresh intact cells. Experimental results also indicate that the content of the peptidoglycan layer, the outer membrane and inner membrane in the cell envelope is in order of inner membrane > outer membrane > PEG layer, while their Cu2+ adsorption capacity is in order of PEG layer > outer membrane > inner membrane. The total contribution of the separated PEG layer material to Cu2+ adsorption is no more than 15% part, and the cell outer membrane and inner membrane contribute about 30%-35% and 25%-30% part, respectively, to Cu2+ adsorption by the cell envelope. The relatively high phospholipid content in the outer wall might result in its higher adsorption capacity to Cu2+, and leads to a higher adsorption capacity of the cell envelope of P. putida 5-x.