The characteristics of circulation and physical quantity of severe coldness in the late spring in Yunnan Province under Kunming Quasi-stationary front during the spring of 2005 are analyzed based on NCEP reanalysis data. The results show that the severe coldness caused by Kunming quasi-stationary front and the upper level shear are related closely to the evolution of circulation, humidity field and vapor transfer, if there is no southern branch trough. The moisture from the northern Burma is converged and uplifted at the middle and lower levels. All these results help to give physic basis of forecast this kind of severe coldness in late spring in Yunnan.