The invention discloses a security reinforcement method for transporting key information in a packet transport network. The method comprises the following steps of 1, determining different transporting paths in information sending and receiving directions; 2, appointing key information interleaving, interweaving and encryption modes by receiving nodes; 3, packaging data to form N data packets and carrying out interleaving to form n new data packets; 4, establishing network connection by sending and receiving nodes; 5, adding MPLS (Multi-Protocol Label Switching) labels and sequence numbers to new data packets; 6, carrying out interweaving and encryption; 7, transporting processed data packets by the sending nodes according to the path of the sending direction; and 8, carrying out decryption, de-interleaving and de-interleaving by the receiving node, thereby restoring the key information data packets. According to the method, through data interleaving, one data packet no longer orderly contains complete data segments and the information contained in the data packets are disordered, even if a transmission link is eavesdropped and the data packets are intercepted, the data is not leaked; and the physical paths of the sending and receiving directions are different, so the security and confidentiality of transmitting the key information in the packet transport network are effectively reinforced.