Using 500hPa grid data over the Northern Hemisphere,the circulation features at the corresponding and earlier stages of the late spring chilling in March over Yunnan are analysed.The results shows that the spring chilling over Yunnan is related with the Ural high pressure ridge and the New Siberian transversal trough changing vertically and at the same time,the southern branch trough over the Bay of Bengal makes Yunnan late spring clilling easily.