The invention provides a processing device for a train network input and output system and a parallel working control method. Two network interfaces and two CPUs are all connected to an Ethernet switch chip; the two CPUs are both connected to a programmable device; the programmable device is connected to a parallel bus interface through a bus driver and is connected to an Interbus interface sequentially through an Interbus protocol chip and a serial transceiver chip; two SPI interfaces are respectively connected to the two CPUs, and an I/O interface is connected to the programmable device, i.e., the integration of two CPU chips in a master-slave working mode or a synchronous working mode on one boardcard is realized by adopting a dual CPU redundancy architecture; a memory is shared betweenthe two chips and arbitration management is realized through a logical chip, so that security and flexibility of the input and output system are effectively improved; and in addition, the problem ofpoor compatibility is effectively solved through the integration of an interbus communication interface and the parallel bus interface.