The invention discloses a method and a computer system for preventing bus transaction from colliding. The computer system comprises a bus, a first main device, a second main device and a processor; the bus comprises a data wire and a clock pulse wire; and the first main device is coupled with the bus. The first main device detects the start stage of a first transaction on the data wire, and when detecting the start stage, the first main device sends an interrupt signal and drives a second transaction of the first main device according to a transaction introduction; the processor is coupled with the first main device and used for receiving interrupt signal, and when receiving the interrupt signal, the processor sends a transaction introduction after certain period of time; and the second main device is coupled with the bus and drives the first transaction to complete within stated time. The invention can avoid the collision between the transactions which non-periodically occupy the busand the transactions of other main device in the bus, so as to avoid unpredictable errors produced by transaction collision and ensure the stable operation of the computer system.