3D reconstruction of ZnO micron ridges was carried out, and the sintering behaviors of these features were studied. Both the grain size and the relative density increase with the sintering time. The densification is through grain boundary diffusion, and the grain growth is through evaporation-condensation. The pore number in the ridges decreases with the pore size increase. Both grain boundary diffusion related flux J(gb) and evaporation-condensation related diffusion flux J(e/c)(g) increase with the sintering time. However, the former is five orders of magnitude lower than the latter, indicating the dominance of the grain growth process in the ridges. Pore shapes evolve from deformed round tubes, to trigonal tubes, and then to deformed flat tubes. The pore surface evolves from a saddle ridge type to saddle ridge plus saddle rut types. The decreasing dihedral angle psi during sintering indicates increased surface energy of pores, consistent with the 3D reconstruction results.