Abstract: The effect parameters, such as fiber2op t ical spo t size, the numerical aperture and magnificat ion of a gradient2index lens,match and assembly betw een a gradient2index lens and the fiber on axial reso lu2 t ion of the fiber2op t ical confocalm icro scope. It is po inted that, in o rder to obtain h igh axial reso lut ion, parameter A related to fiber2op t ical spo t should be less than 3, the h igh magnificat ion gradient2index lens should be selected, the numerical aperture a gradient2index lens should less than that of a fiber, and p recision assembly betw een a gradient2index lens and the fiber should be abtained. Key words: F iber2op t ical confocalm icro scope; F iber2op t ical senso r; Gradient2index lens; A xial reso lu2 t ion