A weather process of cold wave in eastern China in early January 2018 was analyzed, focusing on the role of vertical motion in cold wave cooling through the diagnosis of isentropic vortex and thermodynamic energy equation. The results show that due to influence of the horizontal trough transforming into vertical trough in south of Mongolia, cold-air outbreaks in eastern China. The eastern part of Lake Balkhash and the Siberian region and its northern region are the main sources of cold air that causes this cold wave. Strong cold air associated with high vortex in upper troposphere and lower stratosphere in the northern and polar regions of Eurasia moves south and down along the isentropic direction, leading to strong cold air invading eastern China. The east side of the isentropic vortex large value area corresponds to the rising motion zone, which is conducive to the generation of precipitation. The strong cooling zone is mainly located in the southeast coastal area at 850 hPa by the advection of wind field, and the cooling rate is up to 6×10^-4 K·s^-1 during the cold wave. The cold advection intensity is weak in the northeastern region, and the maximum cooling rate is only about 1×10^-4 K·s^-1 during the whole cold wave. By calculating the average 850 hPa temperature change caused by the wind field advection and vertical motion in the southeastern coastal and northeastern regions, it is concluded that the total temperature cooling rate of both places is about 1×10^-4 K·s^-1. The cooling in the southeastern coastal areas is mainly caused by the cold advection of the wind field, while the northeastern region is caused by the combined of the cold advection and the vertical ascending motion. The cold air in northeastern region can be affected much higher than that in the southeast coastal area in the vertical direction.