In view of the problems existing in multi-focus image fusion, this paper proposes a multi-focus image fusion algorithm based on UDCT (Uniform Discrete of Curvelet Transform). The UDCT is a new mathematical and computational tool for multi-resolution data representation which is also able to provide the higher approximation precision of geometric shape and better sparsely representation ability. Firstly, source images are decomposed at each scale and direction by UDCT to get the UDCT sub-band coefficients. Then, the fusion rule of weighted box-counting dimension in low-pass bands and window-based maximum modulus in directional high-pass bands is adopted. Finally, the fusion image is obtained by using inverse UDCT. The contrast test shows that the proposed algorithm is simple and effective.