In this study, the concentration of six heavy metal ions biosorbed at Hypnum cupressiforme Hedw. (HC), moss determined by voltammetric methods. While determining the optimum biosorption conditions, it was found that the amount of biosorbent 0.1 g, the contact time of metal ions-mosses is 30 min. The biosorption event shows that Ni2+ and Cu2+ appropriate the Langmuir isotherm and sequence of biosorption % was explained for covalent radii of these metals. Pb2+, Cd2+, Co2+, Zn2+, appropriate the Freundlich isotherm model and sequence of biosorption % was explained for the ratio of the hydration number to the hydrated radii of these metals. Biosorption results indicated that HC can be used for removing metal ions from aqueous solutions.