As oxime is selective for Cu2+, oxime groups were introduced to the cell wall of alga by glutaraldehyde. Such modified biomass showed high affinity for Cu2+, which resulted in the increase of copper sorption capacity about 4.5 times higher than that of natural alga. For pH range from 2.5 to 3.0, only Cu2+ were removed by alga biomass modified with oxide, while other heavy metal ions such as Ca2+,Cd2+,Pb2+ were not adsorbed. By changing pH, selective recovery of Cu2+ was achieved