The invention discloses a method for transmitting image bit stream and an image encoder utilizing the method. The image format comprises a start of image (SOI) marker, a start of scan (SOS) marker and a primary compressed data. First, the invention generates redundant data according to a first start address of the SOI marker, a data size between the SOI marker and the SOS marker, and a second start address of the primary compressed data. Afterward, the redundant data is selectively padded into the image bit stream between the SOI marker and the SOS marker. Accordingly, the required time for transmitting image data to a storage medium will be reduced, and the transmission performance will be improved apparently by utilizing the method.