A three-dimensional image analysis system, a process device for use in the three-dimensional image analysis system, and a method thereof are provided. The three-dimensional image analysis system is configured to generate a plurality of three-dimensional data of a three-dimensional image. The process device defines a plurality of horizontal scan lines and a plurality of vertical scan lines according to the three dimensional data, determines a preliminary edge information of the three-dimensional image according to the horizontal scan lines and the vertical scan lines, divides the three dimensional data into a plurality of groups, compares the groups to determine a plane information of the three-dimensional image, and determines an edge information of the three-dimensional image according to the preliminary edge information and the plane information. The method is adapted for the process device.