Stray radiation can be defined as the energy entering the detector through an abnormal imaging path,which will reduce the image contrast and signal-to-noise ratio of the optical system.In severe cases,the energy of stray radiation will directly annihilate the target energy,seriously affecting the normal operation of the infrared optical system.In this paper,the stray radiation characteristics of the transmissive infrared optical system are analyzed,and the suppression measures such as the extinction thread and surface treatment of the objective lens barrel are designed.The effect of suppression measures is analyzed by point source transmittance curve,and the effect of self-emitted radiation of extinction thread is analyzed.Finally,it is verified by contrast imaging experiment,and the results show that the extinction thread has an obvious inhibition effect on the off-axis stray radiation.At the same time,the self-emitted radiation energy of the extinction thread don′t introduce new interference source.