According to the meteorological data of 35stations in North China Plain from 1962to 2011

this study analyzed the variation characteristics of the extreme drought frequency in inter-annual

inter-decadal and its impact factors by using linear tendency estimate

inverse distance weighted interpolation

M-K mutations test and so on.The results are indicated as follows:The extreme drought frequency in North China Plain decreased in the past 50years with a rate of 0.013 5times per year.The changes of extreme drought frequency in spring and summer were consistent with that of all year around

but contrary changes were showed in autumn and winter.The areas where the year-round extreme drought frequency presented increasing trend were distributed scatteredly in the researched area.The extreme drought frequency in North China Plain showed a positive departure in 1962-1969and 1980s

but it was negative departure in other decades. At spatial scale

the areas where extreme drought occurred frequently expanded decade by decade from 1962 to 1989

but they shrunk obviously since 1990s.The areas where extreme drought frequency was comparatively low expanded significantly since 1990sand which covered nearly all the North China Plain since 2000. In recent 50years

the year-round extreme drought frequency in North China Plain changed abruptly in 2003 and the abrupt change in spring

summer

autumn

winter occurred in 1993

1998

1987

2002

respectively. The extreme drought frequency showed a positive correlation with sunshine duration

average wind speed

potential evaporation

average temperature

while it showed a negative correlation with precipitation and relative humidity.