The invention discloses a method of reducing JPEG coding and decoding line buffer capacity. The method is characterized by comprising steps: in a coding stage, as for a frame of read image, image datafrom a 0th line to a seventh line are sequentially written to a coding line buffer module, an address pointer in the coding line buffer module starts from s=0, one is added to the address pointer s when one piece of pixel data is written; after image data of former eight lines are written, the image data are transmitted out according to 8*8 data units needed by the JPEG coding; at the same time,the coding line buffer module starts to write image data from an eighth line to a fifteenth line, and data access scheduling is controlled through controlling a read-write address change logic; and the decoding stage adopts the same read-write address change logic as the decoding state. The above method reduces the required line buffer space by half, power consumption of the chip is reduced, the chip area is reduced, and reduction of product cost is further realized.