Abstract: To investigate the characteristics of weather change in Hainan Island under the influence of strong cold air and further improve the prediction accuracy, based on regional automatic station data of Hainan, conventional observation data and NCEP/NCAR 2.5°×2.5° 4-times daily reanalysis data, and with the synoptic principle and the dynamic diagnosis, the authors analyzed a severe cold weather process affecting Hainan Island during January 22-26, 2016. The results showed that: the polar vortex split toward the south, the ridge in the Ural Mountains fiercely developed so that the cold air could gather in the transverse trough, in front of the transverse trough, the gradient of geopotential height was quite large, and the negative variation of the height was obvious, so was the cold advection, these above mentioned conditions were favorable to revising the transverse trough and moving southwards , which could guide the outbreak of strong cold air southward. The strong cold advection was the main reason of sever cooling in Hainan Island, on the other hand, the shortwave trough was quite active in low latitude area and the warm wet current in front of that could interact with the southward cold air and caused the precipitation.