A three-dimensional system includes at least one pattern projector, at least two cameras, a two-dimensional image feature extractor, a three-dimensional point-cloud generator, and a three-dimensional point-cloud verifier. The pattern projector is configured to synchronously project at least two linear patterns. The at least two cameras are configured to synchronously capture a two-dimensional image of the scanned object. The two-dimensional image feature extractor is configured to extract a two-dimensional line set of the at least two linear patterns on the surface of the scanned object on the two-dimensional image. The three-dimensional point-cloud generator is configured to generate the candidate three-dimensional point set based on the two-dimensional line set. The three-dimensional point-cloud verifier is configured to select an authentic three-dimensional point set correctly matching with the projection contour lines on the surface of the object from the candidate three-dimensional point set.