A new type of leakyannular pupil filter is designed to achieve 3-D superresolution in this paper. Bothtransversal and axial property of this filter are analysed and a simulation example filteris provided which improves 3-D resolution of the imaging system when it is combined withconventional imaging system. Unfortunately, the sidelobe of axial intensity distributionis too high in conventional system. With applying this pupil filter to confocal scanningmicroscope, a good 3-D superresolution is achieved.