The invention discloses a communication network security detection system and a method based on transformer substation information security. The system comprises a network information security detector and several network switches connected to the network information security detector in a mode of mirrorlink. The network switches are connected respectively to each protection device of a remote scheduling terminal and a substation control layer. Communication messages are collected by the mirrorlink from the network information security detector to each switch port. Meanwhile, security and integrality of message information sent from the remote scheduling terminal to the protection devices of the substation control layer are detected. When the message information shows abnormally, the network information security detector sends out warning information to the remote scheduling terminal so as to achieve the aim of comprehensive detection of the communication link security. The communication network security detection system and the method thereof based on transformer substation information security comprehensively detects the communication link security in a mode of intercepting mirror data of the switches by the network information security detector.