Micro CT system is a recently developed imaging technique for small animal, which have very high spatial resolution and sensitivity, and is widely used in drug development, cancer detection et al. But in Micro CT, the artifact, specially the aliasing artifact, become serious as the extremely high spatial resolution, which is the major degeneration of image quality. In this paper, we studied the cause of artifact, and simulated it in computer. Finally, we proposed an algorithm to reduce the artifact in CT slice, with artifact elimination rate of 70% or more, and the improved image contrase