Existing absolute measurement methods take a lot of time to align and adjust the tested flat precisely during the measurement process to ensure the high accuracy. In this paper, we propose a twoflat measurement method that does not require high precision adjustment of the tested flat. The method requires the tested flat measured three times, including the original position, the unknown angle after rotating, and the unknown distance after lateral shifting. The actual rotation angle and shift displacement of the tested flat are solved by feature matching. The surface of the tested flat is reconstructed by the iterative algorithm and Zernike polynomial fitting. Meanwhile, the compensation of the lost angular frequency terms is considered. This method avoids the precise adjustment and shorten the measurement time while ensuring the measurement accuracy. Compared with Vannoni′s method, experimental results show that root mean square (RMS) of the residual of the two measurement methods is 0004λ, and the adjustment process of the tested flat is fast, simple and coherent. The proposed method provides a new way of surface measurement for optical components.