Based on the NCEP/NCAR sea level pressure (SLP) data from 1948 to 2000,the frequencies,routes,interannual and decadal variations of extratropical cyclone activities in both inland and coast areas over East Asia in spring have been analyzed.It is found that in spring (March,April,May),there are three areas where the cyclones occur frequently,in which one area locates to the south of Mongolia High(101°E,45°N),one to the east of Baikal Lake(115°E,53°N) and the other in northeastern China(126°E,53°N).During spring,there are obvious decadal variations of cyclone activity frequencies at the Mongolian cyclone activity center,with less cyclones in 1950s,more cyclones from 1960s to 1970s and less again from late 1970s.To the east of Baikal Lake,cyclones occur frequently in the beginning of 1950s,sluggish from middle 1950s to middle 1960s,more cyclones occur from late 1960s to late 1970s,and then less cyclones occur.In northeastern of China,no clear decadal variations have been found,except that the variation amplitude of the cyclone activity frequencies increases after 1980s.In the eastern coastal area of east Asia,cyclones occur frequently over the regions from the northeast China to far east of Russia and from the Yangtze River to Japan in spring.As for the routes of cyclone activity,only in the area from northeast China to far east of Russia a little difference is found in different periods.Further analysis shows that frequencies of cyclones in north China correlate to the frequencies of sandstorms and rainfall in spring to some extent.