Study is undertaken of the climate base state of northern summer atmospheric action centers and sea level pressure (SLP)with its climate variability and temporal evolution in the past 100 years, indicating that the base state has its high value region of mean square deviation in the Pacific High and Indian Low. The climate base state of the summer SLP exhibits two modes for its variation.The first eigenvector of the base state displays Indian Low, the second Pacific High and Atlantic High.They have secular variation .The Indian Low and Pacific High is enhanced,with the Atlantic High being slightly enhanced in the past 100 years .The climate base state of the Indian Low displays oscillations at periods 80 years.Evidence suggests that the Pacific High and Atlantic High display a remarkably positive trend .They abruptly enhanced in the early 1900s,before that they are considerably weak and after that they become the strongest in 1910s～1930s.Further, the east Asian summer monsoon is closely positively related with the summer Pacific High intensity and with the second mode of northern SLP on the scale of more than 30 years.