With the construction and development of the sites such as the national "MapWorld" recently attracted a growing interest from the scientific and industrial communities, and mainly due to the large number of possible applications capable to provide map service, a crucial issue is arising when dealing with tile map web service publication in copyright protection. According to the need of having a confident and secure communication of tile map in the network environment, a novel mapping mechanism based on watermarking algorithm for tile map is presented here, in such a way that the invisible and robust watermark could be embedded effectively. In the network environment, the geographic data is usually stored in the form of tiles at service terminals, while indexing mechanism is often used as the storage method in order to save the huge amount of tile map. However, the tile map stored by indexing mechanism has different watermarking technology requirements with the common image and raster map data. So, the characteristics and requirements of watermarking technology of tile map stored by the indexing mechanism are firstly analyzed in this paper, which help to apply the watermark embedding and detecting. Then, the meaningless watermark information is generated by m sequence in the process of watermark generating. On this basis, the watermark algorithm based on mapping mechanism for tile map is presented. The watermark information is embedded into the blue channel using the mapping function generated by the red and green channels. The process of watermark detecting is the inverse process of watermark embedding. Finally, the real-time copyright protection system for tile map is implemented and verified experimentally. By experiments, it has been confirmed that the proposed watermark algorithm is robust to cutting, splicing, and additive noise. Besides, the embedding has little effect on the size of original tile map.