An ultra lightweight clamp for three coordinate measuring comprises a support assembly and locating-clamping devices mounted on the support assembly, the support assembly comprising joints and supporting bars, opposite ends of each supporting bar being inserted into a corresponding joint, each locating-clamping device being mounted on several first level joints arranged at the top of the support assembly, the first level joints being each carried by at least three oblique first supporting bars to form a first layer of pyramid-like spatial frameworks, and the first supporting bars each having an lower end inserted into a corresponding second level joint. On the basis of the height of the clamp, the support assembly comprises one or more layers of pyramid-like spatial frameworks, and the joints at the lower end of the bottom layer of pyramid-like spatial frameworks are coupled with feet to be connected to a measuring platform.