Provided are a processing cartridge and a method for mounting a processing cartridge. The processing cartridge comprises a powder compartment part (200) and a waste powder compartment part (100); the processing cartridge is detachably mounted in an electronic imaging device; the electronic imaging device is provided with a protrusion which can expand and contract in the vertical direction; the processing cartridge also comprises a movable part (230); the movable part (230) is movably arranged in the processing cartridge; during the process of mounting of the processing cartridge, the movable part (230) may move relative to said protrusion. A fixed part is replaced by means of arranging the movable part (230); during the process of installation of the processing cartridge, the movable part (230) can move relative to the protrusion such that the protrusion inside the electronic imaging device can no longer be retracted downward in the vertical direction because of the mounting of the processing cartridge.