Abstract: In order to achieve ignition for inertial confinement fusion successfully, it is necessary to reduce the temperature of the ice layer inside cryogenic target by 1.5 K. In the present study, the transient thermal characteristics of cryogenic target during the cooling process were numerically studied, and optimal cooling schemes were proposed to improve the target temperature distribution and to avoid ice quality deterioration. An unsteady numerical model was developed for the cryogenic target based on the Boussinesq assumption and UDF program. The transient thermal characteristics of the cryogenic target during the cooling were analyzed under different cooling rates and schemes. The results show that the maximum temperature difference of capsule increases sharply at the beginning of the cooling, and then tends to be a fixed value eventually. The decrease of cooling rate is conducive to restrain the rise of the maximum temperature difference of capsule and extend the lifetime of ice layer. Delayed cooling with specific delay time can improve the uniformity of the capsule temperature and increase the lifetime of ice layer, and there is an optimal delay time to maximize the lifetime of ice layer.