A processing method for image file includes the following steps. An image file of an image is obtained, in which the image file includes a bit stream and an Exchangeable Image File (EXIF) data. A band indicator and a minimum coded unit (MCU) indicator are read according to an expanded range. A referential DC coefficient is obtained according to a hybrid direct current (DC) coefficient corresponding to a first MCU covered by the expanded range. A sub-clip of the MCU covered by the corresponding expanded range in the bit stream is decoded according to the read band indicator, the MCU indicator and the referential DC coefficient, so as to obtain at least one MCU.