Reactive ion etching characteristics of GaAs,GaSb,InP and InAs using Cl2/Ar plasma have been investigated,it is that,etching rates and etching profiles as functions of etching time,gas flow ratio and RF power. Etch rates of above 0.45μm/min and 1.2μm/min have been obtained in etching of GaAs and GaSb respectively, while very slow etch rates (<40 nm/min) were observed in etching of In-containing materials,which were linearly increased with the applied RF power.Etched surfaces have remained smooth over a wide range of plasma conditions in the etching of GaAs,InP and InAs,however,were partly blackened in etching of GaSb due to a rough appearance.