The invention relates to a wire harness processing tool and processing method. The wire harness processing tool comprises a positioning plate, wherein a routing guide part for providing a guide to a wire is arranged on the positioning plate; and a terminal simulator is also arranged on the positioning plate and has a simulating structure which is used for simulating the arrangement condition of a component terminal. A proper length is reserved at the tail end of the wire according to the simulating structure on the terminal simulator in a wiring process; and the wiring requirements of the actual component terminal can be met in an actual assembly process. Compared with the prior art, the problem that a wire end in a wire harness is over-long or over-short can be solved; wiring is facilitated; improvement of the operation efficiency is facilitated; and the wire harness can be relatively regular.