In order to explore a new method of calculating the operational reliability of rotating mirror by numerical analysis and experiment, a mathematic model of operational reliability of rotating mirror was established by the ANASYS parameter design language, based on the Monte Carlo method and the small sample theory. The result of numerical analysis shows that the value of performance function is further than the value of zero. The correlation coefficient of the maximum stress and the revolving speed of rotating mirror are 0.9, the correlation coefficient of the mirror body density with that is 0.15 and the skewness and kurtosis of the maximum stress, strain and displacement are positive. Meanwhile, the statistical results of the maximum stress, strain and displacement obey normal distribution and show right skewed state. The sample data is concentration appears around the mean value. In the confidence level of 95%, the reliability of rotating mirror is 0.999 9. It can be concluded that the operational reliability of rotating mirror can meet the performance requirement in theory. The maximum stress of rotating mirror is determined by the operational and the density of the mirror body. None of the ten rotating mirror is damaged in the reliability experiment of rotating mirror. The results obtained in the course of this investigation clearly demonstrate that the numerical analysis of operational reliability for rotating mirror is right, which can prove a new method of analyzing the operational reliability with higher practicable and efficient.