Since the large amount of terrain datasets, the terrain visualization component is separated from terrain datasets in spatial application systems in which terrain datasets are stored in the remote server and the terrain visualization component is running on the local host. For this kind of client/server architecture, the server can guarantee the certain response delay and fulfill the real-time rendering of large-scale terrain when the numbers of user are limited. With the numbers of clients quickly increase, the server performance will drop too rapidly to satisfy the client real-time rending need because the server loads are added linearly. This paper proposes a kind of architecture for terrain data transmission in peer-to-peer environment, called PeerTR, which realizes the large-scale terrain data transmission based on P2P by means of the broadband and storage resources of spatial application nodes. In PeerTR, the spatial application node, called TRPeer, is allocated certain size storage space for buffering terrain data received from server and other nodes. Meanwhile, buffers will reserve group member ID lists and the index list of terrain data. TRPeers in the same group share terrain data through exchanging the index lists. A prototype system is established and experimental results showed that PeerTR in performances such as the server’s load and data transmit speed outperforms the mode of Client/Server unicast.