Abstract: As the invariant function for some of the transform has non-denatured, this paper made a research on the watermarking algorithm robust to geometric transformations for geo-spatial vector data. Firstly, the conception and characteristic of invariant function were presented. Secondly, an invariant function robust to rotation, scaling and translation was proposed and proved, then based on the obtained invariant function, by embedding watermark into the geometric invariant, a watermarking algorithm for geo-spatial vector data was proposed. Finally, experiments on the proposed watermarking algorithm were made. The experiments conducted in this paper showed that the proposed algorithm had good robust and could resist attacks such as compressing, adding, deleting, clipping, translating, rotating, scaling and complex attacks composited of above attacks.