The invention relates to the technical field of machining and particularly relates to a collision prevention device and a collision prevention method for wheel machining. After a wheel blank is installed and clamped, a laser displacement sensor is used for scanning the outer contour of the blank and comparing the scanning data with corresponding theoretical data one by one; if the wheel blank is judged to be deflected after being installed and clamped, a machine tool is used for giving an alarm to further analyze the reason; and thus the problem about collision to a cutter is prevented fundamentally.