In this study, we develop a ring laser gyroscope beam precision coupling assembly system to solve the problems of low assembly efficiency and poor quality consistency associated with manual beam precision coupling. Further, we analyze the principle of beam precision coupling with respect to ring laser gyroscope. Thus, the light field intensity of coupling beam is observed to follow a Gaussian distribution. Accordingly, we propose the photodetector pose adjustment method. Subsequently, the optical path change observed during the rotation of the optical prism is analyzed and a method is proposed to adjust the position of the combined prism. Additionally, an adjustment strategy is formulated with respect to the position of the photodetector and the attitude of the combined prism. Then, a beam coupling assembly experiment is conducted on the ring laser gyroscope beam precision coupling system according to the aforementioned adjustment methods and strategies. The experimental results demonstrate that the proposed experimental assembly platform can complete the beam precision coupling assembly task.