The invention relates to a B code time synchronization method based on VPX architecture, and belongs to the technical field of accurate timing. The VPX architecture comprises a power board, an exchange board and a plurality of blade motherboards, and accurate synchronization and timing between blades are the premise of realizing the load balance of the system. Receiving and timekeeping circuits of a B code are implemented on an FPGA of the exchange board, and the FPGA can decode information indicating the second, minute, hour, date, month and year from the input B code. Meanwhile, the FPGA connects a PCIE interface to a PCIE switching chip of the exchange board, and the port is used as an EP. The CPU of the exchange board is used as a RC of a PCIE switching network, and the blades are set as an NT mode. When each NT (blade) requires time synchronization, the current time is required from the EP by an NT port of a PICE bus, and the extracted time is the system time after the time synchronization. Meanwhile, a serial RapidIO interface is reserved in the RPGA, and a RapidIO switch is used as redundancy backup of the B code system. By adoption of the B code time synchronization method, the time synchronization precision can reach a microsecond level, and thus has a very good application prospect in a VPX system.