The invention provides a triple-redundancy 1553B bus dynamic switching method, which includes the following steps: S1, a triple-modular redundancy bus network computer system architecture is built; S2, a redundancy bus configuration method is designed, a bus A for communication is a main bus by default, a first redundancy module is a on-duty module by default when the computer system is powered on, a first bus chip is configured in a BC mode, and a second bus chip and a third bus chip are configured in an MT mode; S3, a bus fault diagnosis method is designed for triple-modular bus real-time fault identification; and S4, a triple-redundancy bus mode composed of a BC mode and two MT modes is reestablished according to the on-duty module switching principle. A spacecraft computer requiring high real-time performance and reliability can determine a triple-redundancy bus fault by using the serial timing characteristic and the information monitoring function of buses. The method is easy to implement, runs reliably, is not affected by the external environment, is quick, and can be easily used in engineering.