In order to accurately and quickly measure the axial gap between each lens in the mirror group, a differential confocal gap measurement method based on five-dimensional automatic adjustment is proposed. This method detects the translation deviation and tilt deviation of the optical axis of the lens group under test according to the spot signal obtained in real time by the CCD detector, realizes the high-precision adjustment of the mirror group according to the deviation information, and realizes the high-precision measurement of the axial gap by using the differential confocal high-precision tomography fixed focus and the internal light tracing of the mirror group. Analysis and experimental results show that the method can effectively improve the attitude adjustment efficiency by 3.4 times, and the accuracy of lens gap repeat measurement can reach 0.53μm. This method provides an effective way to achieve fast and high-precision measurement of lens group gap, and also provides an effective method for rapid and high-precision measurement of various parameters such as center thickness, focal length, and radius of the lens.