1. A geometric structure analyzing method for analyzing a two-dimensional geometric structure of a model composed of at least one magnetic building block, the geometric structure analyzing method comprising: obtaining a magnetic field intensity image of the model, and using a shape of the magnetic field intensity image as a contour of the model; triangularly dividing the contour according to a first algorithm to obtain in the contour a plurality of end triangles, a plurality of normal triangles and a plurality of junction triangles; skeletonizing the end triangles, the normal triangles and the junction triangles according to a second algorithm to obtain a plurality of first skeletons and a plurality of first connecting points corresponding to the model; connecting the first connecting points in the end triangles with one end of each of the first skeletons in the normal triangles neighboring the junction triangles to obtain a plurality of second skeletons and a plurality of second connecting points; and cutting at least one of the second skeletons that is longer than the magnetic building block to form a plurality of third skeletons and at least one third connecting point, and trimming remaining ones of the second skeletons, thereby using the third connecting point, the second connecting points, the second skeletons and the third skeletons as skeletons and joints of the two-dimensional geometric structure of the model.