For error measurement and error compensation of large-scale machine tools in high-end equipment manufacture, a two-dimensional photoelectric level inclination measuring system was established based on the principle of optical auto-collimation and liquid surface reflection to measure the roll angle and the pitch angle of a machine tool. Firstly, a laser diode was used as a source of the system, and the inclination was doubled on the surface of the silicone oil through an optical auto-collimation system. Then, spot position changes were detected by a position sensitive detector, the photoelectric signal containing angle information was output and the four low noise I-V conversion and consistent amplifying circuits were used to amplify signals and to reduce errors. Finally, a high-speed data acquisition system was used to acquire data and to convert them into inclination information by mean filtering, curve fitting and solution processing to accomplish two-dimensional inclination measuriement. A contrast experiment was performed on an optical platform. The results show that the angle errors are less than ±0.050 mm/m (about ±10″) and the linearity exceeds 0.25% within the system measuring range of -10-10 mm/m (about -2 000″-2 000″). It concludes that the system meets the requirements of large range, high precision and high stability and achieves two-dimensional level inclination measurement of large-scale machine tools rapidly.