Abstract: In order to study the frozen sinking process of multi-row holes in deep loose layers of coal mine, the thickness of frozen wall designed according to the requirement of deep formation water and earth pressure is much larger than the actual thickness of frozen wall in shallow layers, which increases the cost of well construction and the construction period. Based on the freezing construction process of the second auxiliary shaft in Dingji Coal Mine, numerical simulation was used to study the effect of changing the cooling time of the outer drainage hole on the thickness of the deep and shallow frozen wall respectively, and the comparative analysis was made with the field measured data. The results show that the best freezing effect can be obtained by postponing the cooling time of the outer drainage hole for 60 days, the average thickness of the frozen wall of shallow stratum decreased significantly, while the average thickness and temperature of the frozen wall of deep stratum still met the design requirements. Time-sharing differential freezing is used to optimize the freezing scheme, which can effectively reduce the thickness of the frozen wall in the shallow strata and the construction cost, and ensured the safe and rapid excavation of the wellbore.