Abstract: In order to improve the speed of obtaining terrain data in 3D terrain roaming systems,an Unstructured Peer-to-Peer Terrain Data Storage System(UPTDS) is proposed on the principle of terrain data characteristics and Unstructured Peer-to-Peer System's virtue.Massive terrain data is stored in the peers of the UPTDS.And UPTDS is divided into two layers,data sever layer and data download layer,according to peer's property and function.The two layers are incharge with data searching and supplying data respectively.Compared with the traditional storage system,UPTDS advances the searching efficiency as well as eliminates server performance bottlenecks.