In this paper, Ti/IrO2-Ta2O5 anodes with different ratios of IrO2 were prepared by thermolytic decomposition method for sulfate electrolysis. The structure and morphologies of the oxide films were determined by XRD and SEM, respectively. Linear Sweep Voltammetry, Tafel Plot and Cyclic Voltammetry were used to characterize their electrochemical activities of oxygen evolution. Test results show that the iridium and tantalum could form solid solution structure. The mutual solubility between iridium and tantalum is affected by the ratio of Ir/Ta in coating solution and influences the dimension parameters of IrO2 crystals. The finer IrO2 crystallites increase on the coating surface and the electrocatalytic capability of oxygen evolution is strengthened with the increasing of IrO2 content in the coatings. When the content of IrO2 is too high, the coating adhesion and rigidity would decrease which affect electrochemical activity of the anode. The electrochemically active surface area is determined not only by the content of IrO2, but also the structure and morphology of the anode coatings. It is probably due to the existence of proper quantities of inert Ta2O5, resulting in a typical morphology of cracks and solid solution structure. The solid solution structure is helpful to prolong the anode service life. The morphology of cracks could perhaps improve the anode active surface area and the electrocatalytic activity of oxygen evolution.