Abstract: Inertial confinement fusion experiment requires the ice layer uniformity of cryogenic target to be less than 1 μm to avoid Rayleigh-Taylor instabilities. For the lack of heating source generated by beta decay of tritium which can force the ice redistribute itself inside the capsule so that the inner ice surface is isothermal, an integrating sphere to forming uniform DD layers with infrared optical fiber source is proposed. The influence of light source position and incidence angle on the temperature field of the cryotarget is numerically studied by coupling the ray tracing and thermal fields. The results indicate that when the power of the infrared light source is 2.25 mW, the incident position is Z=−7.3 mm, the horizontal rotation angle is 157.5°, and the average body heating rate of the ice layer is 24 000 W/m³, the temperature homogeneity of the DD inner surface can meet the requirements of 0.1 mK and achieve the temperature field required for forming uniform DD layers. This study provides theoretical guidance for further experiment of forming uniform DD layers in integrating sphere using infrared radiation.