An assembly auxiliary jig facilitates assembly of an electronic device having a casing, a first fitting, a second fitting, and a wire. The assembly auxiliary jig includes: a base having therein a receiving space for positioning and receiving the casing and an accessing recess configured to communicate with the receiving space and facilitate access to the casing; a first platform disposed at the base and having a positioning groove in communication with the receiving space to thereby receive the first fitting; a first lid hinged to the first platform and configured to close the positioning groove; a second platform disposed at the base and defined with a positioning recess in communication with the receiving space to receive the second fitting; and a second lid hinged to the second platform and configured to close the positioning recess.