Absolute inspection is a high-precision inspection method for optical components, in which the absolute inspection of two flat crystals cannot accurately measure the tilt error in the translation process, which leads to deviations in the quadratic term in the restored surface shape. The liquid level can be kept level before and after the position changes, and there will be no tilt error during the rotation and translation process. The relationship between the tilt error in the translation process and the defocus term in the restored surface shape is deduced and verified by simulation analysis. When there is no tilt error, the residual surface PV value is less than 1nm. The liquid surface rotation and translation interference experiment was carried out on a 300mm vertical Fizeau interferometer. The results were compared with the traditional three-sided mutual inspection method. The surface shape was basically the same, the deviation of PV value was less than 1.3nm, and the deviation of RMS value was less than 0.65nm, it proves that the liquid surface rotation and translation method will not introduce tilt error in the interferometric measurement process.