Rotational laser scanning angular measurement systems have been widely applied in large-scale structural assembly and spatial pose monitoring due to their distributed architecture, high accuracy, and efficiency. However, variations in receiver orientation lead to changes in the beam incidence angle, introducing systematic angular measurement errors that affect the system’s precision and robustness. To address this issue, a local projection model and a Gaussian light-strip distribution model were established based on beam propagation geometry and receiver structural characteristics, and differences in photoelectric response under different incidence conditions were analyzed. Furthermore, by incorporating attitude information provided by an inertial measurement unit (IMU), an effective receiving surface model was constructed in the receiver coordinate system, and an error compensation method considering receiver structural features was proposed. Simulation results show that as the incidence angle increases, the photoelectric response waveform of the receiver becomes significantly asymmetric, with angular measurement errors reaching several tens of arcseconds. The proposed compensation method effectively corrected these errors, reducing the root-mean-square (RMS) error by approximately 90%. In precision turntable experiments, the roundness error of the receiver trajectory decreased from 0.81 mm before compensation to 0.17 mm after compensation, confirming the effectiveness of the compensation model. The study enriches the error modeling framework of rotational laser scanning systems and provides an effective approach to enhance measurement accuracy and robustness under varying receiver attitudes.