The model JQY -800 la3er holographic interferometer is an instrument used for uniformity measurement of large size optical glass by means of double-exposure holographic differential interferometry. The measurement accuracy of ±5xl0~7 can be obtained. The characteristics of structure design are as follows: 1. Foamed rubber is used as vibration-proof leading to a simple construction, Hz vibration can be isolated. 2. The optical path difference introduced by work-table deformation under heavy sample is eliminated, using the method of placing the sample holder at the support point. 3. The sample mount consists of three-dimension angle micro-adjust structure instead of common used ''point, line, plane" positioning structure. It is convenient for machining, assembly, and the requirement of accuracy can be met.