The invention relates to a method for automatically measuring human body dimensions on the basis of three-dimensional point cloud data. According to three-dimensional human body point cloud data acquired by a laser three-dimensional color human body scanner developed on the basis of independent innovation, the original three-dimensional point cloud data is denoised and the like; and then human body dimensions, which are required by costume design, model measurement and the like and comprise height, body measurements and curve length, are acquired by automatically fetching human body characteristic points and characteristic sections. A measuring system adopted by the invention acquires three-dimensional human body outline data, which can reflect the body form of the human body best, by directly scanning the human body; joint points and outline convex points of the human body can be automatically fetched by a maximum and minimum measurement method and a most convex and concave point method; and characteristics and dimensions of the human body longitudinal sections and cross sections can be directly acquired. The method is convenient in operation, high in speed, high in measuring precision, high in repeatability and suitable for human body measurement on a large scale.