Abstract: In this article, the prominent transient characteristic of photocurrent on thermal-formed iron oxide electrode was discussed. This accounts for the fact that photocurrent values measured with lock-in amplifier greatly exceed their average algebraic values. The photoresponse of anodic-formed iron oxide passive film is similar to that of thermal-formed with some differences. Our present experimental technique is still insufficient for monitoring structural changes of film during the formation of the latter. Nevertheless, our results showed after the film was principally formed, photocurrent is proportional to film thickness. Before this period, there is a positive deviation of photocurrent and the linear relationship does not hold.