In order to analysis the effect of micro-arc oxidation time on the structure of the porous titania films prepared by a composite oxidation (that is pre-oxidation and micro-arc anodic oxidation), the SEM, EDS, XRD and micro-hardness testing methods were employed to investigate the phase constitutes, element compositions, morphologies and hardness of the modified films. The results show that micro-arc oxidation time is one of the major factors influencing the morphologies, structures, hardness and the ratio of Ca/P of the coatings treated by the two-step anodic oxidation treatment. With the micro-arc anodic oxidation time increasing, the diameter of the pores, roughness of the surface, hardness all increase, and the atomic ratios of Ca/P are changed at the same time. The rutile phase in the coatings become more and anatase become less when the time varied to a long period. So appropriate porous titania coatings can be gained by adjusting the micro-arc anodic oxidation time in the composite oxidation method.