A database query system is provided. The database cache system includes: a network library which processes an access request issued by the online game server by using an input output completion port (IOCP); at least one database connection module which provides a connector for reading data from the database or recording data to the database; a database cache which stores data read from the database by the database connection module; and at least one cache buffer which is allotted to an IOCP worker thread corresponding to a database query request issued by the online game server and stores data read from the database, which is to be transmitted to the online game server.