A telephone switching network quantum encryption system and an encrypted communication method are disclosed. The encryption system includes a total amount sub-generation management system, a total PSTN domain and a total IMS Domain Quantum VPN, a PSTN domain and an IMS domain quantum generation management terminal of a plurality of regions, and a PSTN domain and an IMS domain quantum VPN of the plurality of regions. Based on the system, the communication between the IMS domain phones of the State Grid Corporation, the PSTN domain phones, and the IMS domain phones and the PSTN domain phones canbe encrypted by the quantum encryption means of the data packets.