The invention discloses a database synchronization method and system. The method comprises the steps that a main database and a sub-database are divided into a plurality of zones, and each main data zone and each sub data zone are respectively provided with a main binary system journal file and a sub binary system journal file. When data changing happens in the main data zones, data changing is recorded in the main binary system journal files, the data changing record is transmitted to the sub-database, data changing is recorded in the sub binary system journal files, and data changing is carried out in the sub data zones of the sub-database. According to the method and the database system, the database is divided into the zones, the binary system journal files are arranged corresponding to the database zones, multithreading concurrent processing binary system journal file synchronization is used, and the problem that during a binary system journal file synchronization process, database end playback is slow, and database end system resource using rate is low is solved. In addition, data of the main database is transmitted to the sub-database end in a batch mode, and data lost from the sub-database end are reduced as much as possible.