In early 2008， most areas in south China experienced extreme low temperature， heavy rain， snow， and freezing weather. This extreme weather had great influence and threats on the stable operation of power systems and power supply. This paper introduces the main situation and characteristics of the wide area blackouts in Guizhou， Guangxi， Yunnan and Guangdong provinces in south China. The main developing process of this ice and snow disaster in 500 kV main power grid is illustrated， and the typical characteristics of the main power grid subjected to this disaster are summarized， then the problems exposed in this ice and snow disaster are analyzed from many aspects， such as long distance large capacity transmission line proportion， the power supply and power grid planning， and the 500 kV transmission line corridor selection etc. Some solutions and suggestions on power supply development and power grid structure of 500 kV main power grid are proposed to improve the anti-disaster ability.