In order to meet the high resolution、high accuracy of environmental detection,to improve the detection capability in complex environment and to solve the problems that the conversion speed of the optical path was slow for multi-band optical system and there were differences in the object information of different bands,an optical system that features visible light,medium / long-infrared light,shared aperture,con-focal was designed.The system can receive target informations of three bands at the same time.The focal length for visible、medium / long-infrared light is equal by focal length compensation,which improves the consistency of target information for three bands. The focal length is 12 mm and field of view is 36°.The transfer function value is >0.53 for visible light at 80 lp/mm Nyquist frequency;the transfer function value is >0.5 for mid-infrared light at 20 lp/mm and the transfer function value is >0.36 for long-infrared light at 20 lp/mm. The system has an excellent overall image quality and is athermal for temperatures between -40 °C and +60 °C.