One course radius measurement method for vertical petroleum tank volume metrology based on 3D laser scan principle was researched. Method of distance measurement by laser phase-shift technology and angular measurement by optical grating was applied to acquire coordinates of points in each course under the control of servo system. The permitted error of measured point location is 2mm. Fitting algorithms base on direct iterative method (DIM) and least square method (LSM) were used to process measured data and deduce equivalent radius of each course. In comparison experiment, one 1000m3 vertical tank was used as test object. Compared to strapping method (international mandatory standard), the maximal deviation radius value of method discussed is 2.8mm. The maximal difference of radius value calculated by DIM and LSM is 0.1mm. The experimental results verified the method discussed in this paper.