Using conventional observation data and NCEP reanalysis data, the causes for unstable conditions of a strong convective weather under the background of the cold vortex in Shenyang City of Liaoning Province were analyzed by studying four kinds of CAPE and the relationship of CAPE field and surface meteorological factors. The results show that the water vapor latent heat is the main part of the unstable energy. Under the background of the cold vortex, the low level warm and moist advection, and high level cold and dry advection were advantageous to unstable energy accumulation, which leads to the occurrence of strong convective weather. The convective temperature CAPE can refect the unstable energy required by the afternoon strong convective occurrence, and it has a certain significance to the forecast of strong convective weather.