By using the conventional observation, and the radiosonde, satellite, radar, wind profile, NCEPFNL analysis data as well as the data of three deterministic global forecast systems, causes of rainfall and forecast biases of two cold vortex rainfall events in 2017 over North China are comparatively studied. The results show that the event that occurred on 22 June 2017 is characterized by persistent and steady rainfall with weak rainfall intensity and lower convective height. The rainfall echo is of convectivestratiform mixed type. However, the rainfall on 6 July is shorttime severe rainfall and the height of convective echo top is very high. The background conditions are quite different between these two cases. For the 22 June event, cold vortex is at its mature stage and subtropical high is far south. Moreover, a warm section convection occurred on the previous day, and its cold pool is quite strong, leading to the release of convective energy, thus the convective energy and water vapor are normal for the first case. Comparatively, for the second case the cold vortex is at its developing phase and subtropical high is located more northward.By using the conventional observation, and the radiosonde, satellite, radar, wind profile, NCEPFNL analysis data as well as the data of three deterministic global forecast systems, causes of rainfall and forecast biases of two cold vortex rainfall events in 2017 over North China are comparatively studied. The results show that the event that occurred on 22 June 2017 is characterized by persistent and steady rainfall with weak rainfall intensity and lower convective height. The rainfall echo is of convectivestratiform mixed type. However, the rainfall on 6 July is shorttime severe rainfall and the height of convective echo top is very high. The background conditions are quite different between these two cases. For the 22 June event, cold vortex is at its mature stage and subtropical high is far south. Moreover, a warm section convection occurred on the previous day, and its cold pool is quite strong, leading to the release of convective energy, thus the convective energy and water vapor are normal for the first case. Comparatively, for the second case the cold vortex is at its developing phase and subtropical high is located more northward.