The invention discloses a local network system and a method for maintaining the safety thereof and belongs to the field of network safety. The system comprises network monitoring equipment, a safety terminal, a main control server, public / private secret-associated source servers and a protective server, wherein the safety terminal, the main control server, the public / private secret-associated source servers and the protective server are connected with the network monitoring equipment; the network monitoring equipment monitors data switching and forwarding; the safety terminal performs local monitoring; the main control server verifies identity and maintains safety policies; the public secret-associated source server monitors accesses to the public secret-associated sources; the private secret-associated source server monitors the accesses to private secret-associated sources; and the protective server provides data reduction protection. The method comprises the following steps that: the safety terminal inputs authentication data and input modes; and the main control server verifies the identity of a user; and if the user passes through the verification, the main control server, the network monitoring equipment, the public secret-associated source server, the private secret-associated source server, the protective server and the safety terminal jointly maintain the safety of the network. The system and the method improve network access safety.