The utility model relates to the field of medical equipment, be a supplementary guiding device of C arm machine multi -angle laser very much. The utility model discloses a fix on the main arm of C arm machine and along the backbone of its extended length orientation setting, first slider, messenger that at least one can freely move on the backbone win the locking mechanical system that keeps locking relatively or remove the locking between the quick -witted main arm of slider and C arm and with a slider rotationally connected's a laser locator, a laser locator rotation centerline is perpendicular with the main arm place plane phase of C arm machine, be equipped with still between a laser locator and the first slider that can make wins keeps locking relatively or removing the 2nd locking mechanical system of locking between a slider and the laser locator. The utility model discloses can assist C arm machine to carry out accurate location to scanning portion bit position, the degree of depth, angle in the art when scan.