Since cryogenic optics can reduce thermal noise and improve the signal-to-noise ratio of detection systems, it is the necessary way to implement high sensitivity infrared detection. A cryogenic refractive optics which uses a pulse tube cryocooler as its cold source is proposed. This new cryogenic optics can be used in the occasions where volume and weight are limited and high-sensitivity infrared detection is required. The design process of the cryogenic optics is described in the aspects of optical design, opto-mechanical structure design and internal thermal noise analysis. A test system for verifying the feasibility of cooling optics by pulse tube cryocoolers is built and the effectiveness of the cryogenic optics is verified in the aspect of the thermal noise in the detection system. The experimental results show that the temperature of the optical components drops to 150 K from room temperature in three hours and can further drop to the lowest temperature 105 K. In the test process, the lens is well preserved, which verifies the feasibility of using a pulse tube cryocooler as the cold source. A blackbody and a 320× 256 pixel HgCdTe array detector are used to test the thermal noise of the optical system. The results indicate that the thermal radiation is decreased by 75% when the temperature of the optical system drops from 300 K to 215 K. This is in good agreement with the theoretical analysis result. It demonstrates the effectiveness of reducing noise for cryogenic optics.