The liquid volume is an important metrology method for commercial transaction in international trade, and the vertical tank is used as main metrology tool. One non-contact optical measurement system was raised by using laser scanning method. The coordinates of vertical tank shell were acquired by phase-shift ranging method and angular measurement, and the set of coordinates is named as data cloud. The deformation of the vertical tank not only affects the daily use and safe operation, but also influences the accuracy of the tank volume measurement. Based on the 3D laser scanning principle, one measurement method for the vertical tank deformation was introduced. By using the high-resolution analysis model, the overall and local deformation of the vertical tank were measured simultaneously. The measurement errors of distance and angle are 2mm and 2″ respectively. Iterative method was used to deduce the radius at each course height for tank model without deformation. One experimental system was designed and the method was validated by experimental data.