Ways of electrochemicals modification surface semiconducting electrode based on gallium arsenide (GaAs) was proposed in this work/ Behavior of unmodified and modified GaAs was investigated characterization was identified (steepness of electrode function, working interval? responses time, reproducibility). Possibility of using electrodes from GaAs for potentiometric titration of ions Cu2+ and Pb2+ was set. Modified GaAs-electrodes has improved electroanalitical characterizations in variants direct potentiometric titration was shown.