A pupil filter is a useful technique for modifying the light intensity distribution near the focus of anoptical system to realize depth of field (DOF) extension and superresolution. In this paper, we proposeda new design of the phase only pupil filter by using Zernike polynomials. The effect of design parametersof the new filters on DOF extension and superresolution are discussed, such as defocus Strehl ratio (S.R.),superresolution factor (G) and relative first side lobe intensity (M). In comparison with the other two typesof pupil filters, the proposed filter presents its advantages on controlling both the axial and radial lightintensity distribution. Finally, defocused imaging simulations are carried out to further demonstrate theeffectiveness and superiority of the proposed pupil filter on DOF extension and superresolution in an opticalimaging system.