The method is applicable to a computer system accorded with PCI - Express protocol. The computer system includes a bus coupled to a terminal device. The method for reading data includes following steps: based on a reading request from the said terminal device, obtaining a first data; then, in a transfer waiting cycle, fetching out data accorded with length of first data from first data, packing data accorded with length of first data to a data packet in transmission layer; length of data packet in transmission layer is changed to length of first data from a prearranged length, where the length of first data is larger than the prearranged length; the transfer waiting cycle is happened when bus is involved, sequence of feedback data generated in disorder, or data packet of other virtual channel transferred on the bus at present. |