Computer mainboard and starting method thereof

A computer mainboard comprises a first composing unit, a second composing unit and a BIOS BIN file; the first composing unit comprises a ROM chip and a system chip; the BIOS BIN file is loaded in the ROM chip; the BIOS BIN file comprises a starting module, a joint module and a plurality of loading modules corresponding to the mainboards of different types; the starting module judges the types of the mainboards through judging the PWL signal of the idle GPIO pin of the system chip and reads the loading modules corresponding to the types of the mainboards and the joint module; the joint module is used for detecting and initializing the first composing unit; the loading modules are used for detecting and initializing the second composing unit. The invention also provides a starting method for a computer mainboard. The BIOS BIN file can be used on the mainboards of different types of the same chip set, thus reducing the repeated work and the maintenance work of the research personnel, thereby reducing the develop