This paper describes the principle about the imaging system of the stereo endoscope. The system adopts two optica] channels stereo imaging technique to replicate human binocular vision. It employs time multiplexing art accomplished by images processor. By an active matrix liquid crystal screen and a circular polarized eyewear the synchronous separation of the left and right images will be shown. So this system can present strong stereo-inspection. This paper analyses and compares three methods of optical system. This paper also briefly introduces the application of this system in mini-invasive surgery (MIS) and measuring field.