Abstract: A composite sine-trapezoidal fringe structured light 3D measurement method includes projecting trapezoidal fringe patterns onto a measured object and capturing fringe images; sorting the fringe images by brightness, resolving them into uniform light images and sinusoidal light images, and obtaining a sub-region ordinal number of each image; using the uniform light image to identify a strength response model of the captured fringe image, and obtaining a strength response model parameter; an actual projection strength, a sub-region phase of the sinusoidal light image according to the actual projection strength, a wrapped phase according to sub-region phase and sub-region ordinal number, an absolute phase according to the wrapped phase and sub-region ordinal number, a surface point of the measured object at the positions of a projector pixel and a camera pixel according to the absolute phase, and an object surface model of the measured object by a reconstruction by triangulation.