The invention discloses an aircraft engine duct shape detection method. In the method, an air craft engine duct shape measurement and positioning device is involved, and comprises a length positioning device and an angular positioning device. The detection method comprises the following steps of: arranging a duct on the length positioning device, scribing the duct according to a straight line segment length determined by a UG model of the duct, and then cutting the duct off according to scribed positions; and arranging the cut-off duct on the angular positioning device, regulating an angle head by rotating the angle head to an angle consistent with the UG model, and positioning duct fittings with angular requirements by pins. The detection method has the advantage of solving problems on the accurate length positioning of bent pipes and the accurate angular positioning of the duct fittings, along with simple structure and easy operation.