Abstract: Physicochemical and electrochemical performances of long service life Ti/70％IrO230％Ta2O5 (mole fraction) anodes prepared at 450 ℃ have been investigated over the whole electrolysis time in H2SO4 solution .The results showed that the whole electrolysis process of this anode could be divided into three stages consisting of ‘active',‘stable' and ‘deactive' ones.In the first two stages,the dissolution of coated oxides was dominated (with preferential loss of IrO2 component).It was found that,in these two stages,the preferential orientations of (110) and (101) planes in IrO2 rutile decreased with the electrolysis time,and that of (002) plane increased,while the preferential orientations remained to be stabilized in the ‘deactive' region.This indicated that the loss mechanism of the catalyst coatings was changed.Electrochemical impedance spectroscopy (EIS) measurements showed a slight increase in oxygen evolution reaction resistance of the oxide catalysts while a sharp rise in totally physical impedance of the whole anode in the ‘deactive' region.Xray diffraction analysis (XRD) showed that the intensity of TiO2 rutile reflections increased with the electrolysis time,with a sharp increasing in ‘deactive' region.According to the experimental results the degradation mechanism for long service life Ti based coating anodes has been proposed.