Abstract: In order to orientate a non-orthogonal shafting laser theodolite measurement system quickly and accurately, a construction technology of variable-length photoelectric reference scale was proposed based on high-precision photoelectric position sensitive detector . Firstly, the feature of a non-orthogonal shafting laser theodolite was elaborated. According to the features and the orientation requirement of a non-orthogonal shafting laser theodolite measurement system, the general idea of the construction of variable-length photoelectric reference scale was confirmed. After that, the design of hardware circuit was finished and a variable-length photoelectric reference scale was constructed. Finally, spatial position relationship between two photoelectric position sensitive detectors was calibrated to realize the measurement of variable-length reference. The experiment results show that the relative measurement accuracy of variable-length photoelectric reference scale is better than 0.03%. The orientation of a non-orthogonal shafting laser theodolite measurement system can be realized conveniently and in high-precision.