The invention provides a five-axis side milling 
machining cutter path 
smoothing method. The method comprises calculating the initial 
cutter location, and calculating the 
machine tool turning axle angle corresponding to the direction of a cutter axis through a dynamitic model of a specific 
machine tool; performing interpolation for the 
machine tool turning axle angle of the initial 
cutter location and the cutter 
nose point location, and obtaining a cutter 
nose point location trajectory and a 
machine tool rotation angle change curve; according to the cutter 
nose point location trajectory and the cutter axis vector, showing a side milling 
machining cutter path; calculating the 
rigidity matrix, corresponding to the cutter path, of the 
machine tool rotation angle curve; according to a 
differential evolution algorithm, calculating the point that the distance between the point to the cutter enveloping surface is shortest among the points on the design surface; and according to a weighted least square method, establishing a five-axis side milling 
machining cutter path 
smoothing model, and obtaining an optimized the initial 
cutter location and the cutter nose point location curve and a smooth 
machine tool rotation angle curve after solution. The five-axis side milling machining cutter path 
smoothing method solves the problem about smoothing and geometric deviation control of the five-axis side milling machining cutter path, and is suitable for five-axis side milling machining on a 
free form surface, a ruled surface or a curved surface similar to the ruled surface.