Photonic crystals (PCs) have many potential applications because of their ability to control light-wave propagation. We have investigated the focusing of electromagnetic wave propagation inside an anisotropic PC slab by means of finite-difference time-domain simulations. The PC structure composed of air cylinders in the anisotropic-dielectric medium is studied by solving Maxwell's equations using the plane wave expansion method. Numerical simulations show that the optical imaging resolution can be improved greatly in the square lattices consisting of anisotropic-dielectric background. Such a mechanism of negative refraction PCs should open up a new application for designing components in optical imaging systems.