Abstract: Stringent attitude determination accuracy is required for the development of the advanced space technologies and thus the accuracy improvement of digital sun sensors is necessary. In this paper, we presented a proposal for measurement error analysis of a digital sun sensor. A system modeling including three different error sources was built and employed for system error analysis. Numerical simulations were also conducted to study the measurement error introduced by different sources of error. Based on our model and study, the system errors from different error sources are coupled and the system calibration should be elaborately designed to realize a digital sun sensor with extra-high accuracy.