With the continuously emerging of Internet applications based on secure group communication, the design of secure group communication becomes an important Internet design topic. Group key management is important for secure group communication. Previous work focuses on key tree, which is an important type of key graphs. In this paper, we first propose another type of key graph-key link-tree, which shows better performance than key tree in single rekeying. Considering that the adoption of key link-tree results in worse than key tree in batch rekey, we propose two transform algorithms between key tree and key link-tree, which can get better rekey performance.