In optical systems, in addition to their imaging function, some kinds of prisms, (e.g., cube prisms), can be used for target tracking or image stabilizing. Therefore, prism systems have been widely applied to various optical systems. To simplify the optical system, cube prism assembly can simultaneously act as a tracking and stabilizing element. This article deals with a two-cube prism assembly in collimated light, which has LOS stabilizing and target tracking functions when finite angular perturbation exerts on the optical device. Because there is no simple relation between change of the image space and the rotations of the prisms in the case of a finite angular perturbation, a microprocessor is used for controlling the rotations of the prisms. Such a microprocessor controlling the LOS stabilizing and tracking experimental device is manufactured, consisting of a telescopic optical unit, two-cube prism assembly, microprocessor (Z80) data processing and controlling unit, gyro attitude sensing and data sampling units, and a stepping motor acting unit. The experimental results show that the two- cube prism assembly can simultaneously meet the demands of target tracking and LOS stabilizing in the case of a finite angular perturbation. On the other hand, in order to reach the real-time LOS stabilizing effect, higher speed microprocessor and data sampling units are needed.