Abstract: The sealing performance of system devices in cryogenic environments is very important. It is necessary to grasp the flow characteristics of small leaks at low temperatures for cryogenic sealing research. In this paper,a microchannel with random roughness walls is constructed,and simulation software is used to study flow characteristics of the leaking microchannel in liquid helium temperature to calculate and analyze the distribution and changes of physical quantities. The results show that the wall roughness has the greatest impact on velocity distribution near the wall,the impact decreases gradually away from the wall,and it has almost no effect on the flow in the central area. Hypothermia causes the helium viscosity coefficient to decrease,and the velocity of gas flow increases.Pressure distribution also fluctuates due to changes in channel characteristic dimensions. The mass flow rate of the leak in the liquid helium temperature is two orders of magnitude larger than that at room temperature,and the mass flow rate does not change when the ratio of inlet and outlet pressure exceeds the critical value. It has theoretical significance and practical value for leakage prediction,leakage prevention,leakage detection,and sealing research of cryogenic systems.