In order to achieve the in-situ calibration of the measurement of angle between bifacial lines in large-scale space, the calibration approach based on target is proposed. A practical engineering project is taken to introduce the measuring principle, and in-situ calibration strategy which is suitable for quickly implementation is presented. The error sources of measurement system are analyzed and the design proposal of system calibration board is proposed. The reasonableness of framework design and layout of calibration board is checked. The digital image processing algorithm of calibration is designed, and the result of each step is proposed. Experiments indicate that the mean error of the visual inspection system is reduced from 0.065123° to 0.00219° using the calibration method with the illumination condition of 355 lx. The effect of error compensation meets the requirement, and the standard uncertainty of measurement for the angle of bifacial lines separated at a distance of 7 m is 0.114°.