The numerical simulation using the NCEP/NCAR 1°×1° global reanalysis in January 2008 and the MM5 mesoscale model is performed to investigate the stru cture and characteristics of Kunming quasistationary front (KQSF) during the extrem e low temperature and frozen snow events over southern China. The results indi cate th at the formation and its maintenance of KQSF are the consequence of the obstruct i on due to plateau terrain and special synoptic system configuration under the i nflu ence of the longtime, repeating cold airs over southern China. It is foun d t hat the obstruction of plateau terrain is necessary for the formation and the ma intenance of KQSF by the sensitivity numerical experiments of halving terrain.