A method for changing an avatar in an online game includes: generating an avatar self-defined data packet comprising complete data of an avatar according to an avatar characteristic self-defined data packet from a client corresponding to a logon account, wherein the avatar characteristic self-defined data packet reflects modification or creation made by a player to the avatar; and transmitting the avatar self-defined data packet to the client corresponding to the logon account providing the avatar characteristic self-defined data packet, and/or a second client participating in the online game. A system and an apparatus for changing an avatar in an online game are also provided.