Lateral shearing interference has such unique merits in optical testing, (1) anti-shock, (2) reference spherical surface is unnecessary. (3) the ratio of intensity of two beams is 1:1 in any case, (but in ordinary interference, the ratio of intensity of two beams isn't always 1:1 in any cases, because its ratio can be change according to different testing condition, in some cases maybe it is 1:25, so the interferogram is vague). But its interferogram is different from ordinary interferogram for same tested wavefront (so the experience for testing ordinary interference isn't applied to shearing interference completely). That is to say, the position and the amount of the error wavefront can't be taken clear, even if for the same tested wavefront, the shearing interferograms aren't same completely, when using different shearing distance. The quantitative process just solves this problem through two shearing interferograms whose shearing directions are normal to each other so the real error condition of tested wavefront can be calculated. The calculation can use two different ways, that is: Transposition Zernike Coefficients Method and Extended Simultaneous Equations Method. At last showing 2 types shearing prisms. We can use it to get two shearing interferograms at the same time and to change the shearing distance arbitrarily.