A wire stripping knife comprises a handle having one end provided with a hanging portion to be hung to a desired position, and the other end fixed with a blade. The end of the handle, which is fixed with the blade, is pivoted with a clamping member. One end of the clamping member, which is adjacent to the blade, is provided with different-sized stripping notches. The handle and the clamping member each are provided with engaging portions for mutual engagement. The distal end of the blade is formed with a cutting surface vertical to the cutting edge for cooperating with a guiding plate at one end of the clamping member to strip off the insulation more quickly with high safety.