A laser heterodyne interferometric straightness measurement apparatus and method with six DOFs determination includes a part for determining the straightness and its position based on laser heterodyne interferometry and a part for error determination and compensation. The optical path for determination of four DOFs errors including three common beam-splitters, a polarizing beam-splitter, a planar mirror, a convex lens, a position-sensitive detector and two quadrant detectors is added in the optical configuration of the part for determining the straightness and its position based on laser heterodyne interferometry.