As an optical focus detection technique, confocal microscopy has been received much attention in the last few years. It has not only the particular property of depth discrimination, but also the ability of enhancement of contrast by suppression of light scattered from defocused object location. Therefore, the techniques based on confocal microscopy have been developed as a powerful tool for surface profiling. However, in order to maintain the high resolution, it is difficult to make fiber-optic sensor as small as possible, and which restrict the measurement of small internal curve surface. For the purpose of uniting micromation and high-precision in profile, based on a fiber confocal microscopy theory, a new fiber optical scanning microscope made up of splitter and GRIN lens is presented. Compared with other confocal technique, it has smaller size, higher anti-jam, and higher axial resolution. Especially, it has the characteristic of absoluteness zero point, which can be used for 3D and super-glossy inner surface profile. Experiment results show that the axial resolution with 30nm and linearity range 40μm can be achieved. This linearity, high resolution and small cubage permit non-contacting surface profilometry to be readily obtained for specimens of uniform reflectivity and small internal curve surface profile.