The invention relates to an image processing box in an electrophotograph imager which includes an fixing unit and a developing unit and a sensitometric drum box, the photosensitive drum box and the developing unit can be dismountable assembled, and the image processing box further includes an encoding device that is used for transmitting status identifying information to the electrophotograph imager, the encoding device is composed of a plane mechanism and realizes straight line reciprocate of a signal blocking patch in the encoding device. The image processing box uses the technique scheme, the contained encoding device uses the plane mechanism that the components motion trail has high accuracy, therefore, the nontransparent blocking patch has more precious testing time through a code reader, can ensure the image processing box always being correct identified with more accurately and effectively compared with encoding wheel device driven by torsional spring coupling device.