Axial resolution in optical coherence tomography (OCT) imaging is determined by the coherence length of light source and the beam-focusing condition. The most adopted approach for achieving high axial resolution in OCT is using a light source with a broaden bandwidth. A method to increase the axial resolution in OCT by combining coherence gating with apodization through an appropriate pupil filter is introduced. In the proposed OCT system, the width of central lobe of axial point spread function is apodized to be within the coherence length of light source, while its side-lobes are lying outside without contributing to coherence imaging. It is in this way that improved resolution can be obtained in OCT system without recurring to broadening the bandwidth of light source, which is nevertheless costing and inconvenient in implementation.