Biosorption of several heavy metals including that zinc, cadmium, mercury and copper on Entromorpha as green alga was investigated. The Henry single parameter isotherm model and also both the Langmuir and the Freundlich as two parameters isotherms have been studied in the constant conditions with respect to the presence of operating parameters such as initial biomass dosage, temperature, initial pH, initial metal ion concentration and contact time. The results from atomic absorption measurements shown that the Freundlich isotherm model are more promise than the Henry and the Langmuir isotherm for Biosorption of zinc, cadmium, mercury and copper on Entromorpha. Therefore, we are encountered with heterogeneous, reversible and multilayers biosorption.