In this paper, we analyze the process of coherent anti-Stokes Raman scattering (CARS) based on quantum theory and set up a traditional point-scanning CARS microscope. With this microscope, high-contrast images of polystyrene microspheres are obtained. By scanning polystyrene beads with 110 nm diameter, we reconstruct the point spread faction (PSF) of the system. And the full width at half maximum (FWHM) of the PSF shows a lateral resolution about 600 nm, which is larger than the theoretical value (～ 300 nm). Therefore, we propose several resolution-improvement approaches, which lay a strong foundation for the realization of nano-CARS microscopy.