Abstract: Digital watermarking algorithms for vector digital maps are an efficient method to counter abuses of the maps.We analyzed current methods of watermarking for digital vector geo-data and presented a new robust blind watermarking approach.The proposed algorithm starts with the area subdivision,then watermarking is embedded into length of vector by changing some x coordinates or y coordinates.The experiments show that the proposed algorithm could effectively resist the attack of noise,removing points,adding points,deleting points,and so on.