In order to solve the traditional confocal microscopic system could not have the resolution and linear range of problems, a confocal microscopy techniques is put forward, based on the technology of variable optical path using the optical path of the modulation. The single parameter is different from coke response curves can be obtained, The multi-differential optical path system with absolute zero and good linearity is realized, so as to realize the compatibility of high resolution and large range in the same system. The technology reduces the performance difference of components and artificial adjustment error. The structure is simple and the reliability is improved. The experimental results show that the system canhavebothresolution andlinearrange, and the axialresolution can reach 6.46 nm. It provides atechniquewith highprecision, simplestructureandwideapplicationforthemeasurementoffinestructure.