The invention discloses a cutting force simulation pre-adaptation cavity outer corner numerical control milling machining tool path optimization method which concretely comprises the steps that step one: tool path and workpiece information is inputted and outer corner parameters are acquired; step two: the innermost cutting layer of the outer corner is optimized; step three: the rest cutting layers are optimized; step four: the cutting layer contour radius of the other side is calculated; step five: the position and the start and end points of all the cutting tool paths are determined; step six: a non-cutting moving tool path is added and a complete local cycle is generated; and step seven: the optimized tool paths are outputted through combination of the original tool paths. The machiningmode of local cycle layer cutting is adopted so that the cutting force heat is enabled to be equalized and the load impact can be reduced; the optimized tool paths are composed of arcs and straight lines and smooth transition between cut-in and cut-out can be realized so that the vibration can be effectively reduced and the machining surface quality can be enhanced; and the excessively high forceheat load can be avoided by constraining the maximum cutting width.