The invention provides a catadioptric astronomical telescope with a bifocal system. On-axis and off-axis aberrations are corrected well through a special optical path system, the length of a lens coneis short, and a long focus and a short focus are achieved on one lens cone. The catadioptric astronomical telescope comprises a main refractor 1, a main refractor 2, a main reflector and a main refractor 3 which are located on the same optical axis. The main refractor 1 is a plano-convex positive lens with a hole formed in the center, a lens base of the main refractor 3 is installed at the hole formed in the center of the main refractor 1, and a catadioptric lens set or a convergent lens set is detachably connected to the lens base of the main refractor 3. The main refractor 2 adopts a plano-concave negative lens. The main reflector is a plano-concave lens with a concave surface as a reflecting surface, a hole is formed in the center, and a convergent lens is arranged at the hole in the center of the main reflector. The catadioptric lens set is an assembly formed by integrating an auxiliary refractor and an auxiliary reflector. Under the condition that the long focal length is used, the main refractor 2 refracts light three times in a light path, the main refractor 3 and the auxiliary refractor refract the light two times, and under the condition that the short focal length is used, the main refractor 2 refracts the light two times.