The invention provides a two-
bus data transmission method, which is applied to a
master station machine, and comprises the following steps that: the
master station machine responds to a
preemption communication frame which is sent by a slave
station machine in a code returning area of a request
preemption time domain and carries a request
preemption signal, and sends a response communication frame which carries a
bus state response
signal in a code sending area of the request preemption
time domain; the
master station machine receives an event communication frame which is sent by the slave
station machine in a code returning area of the event competition
time domain and carries an event competition
signal, and the event communication frame is generated after the slave
station machine judges that the request is allowed to be preempted according to the
bus state response signal; the main station machine generates an event competition result signal according to the event priority; and the master station machine sends a two-bus distribution communication frame carrying an event competition result signal in a code sending area of the event competition time domain so as to notify the slave station machine to reserve competition for the two buses according to the event competition result signal, so that the slave station machine reports an event according to a competition reservation result of the two buses.