Based on the NCEP/NCAR reanalysis data, the sea level pressures(SLPs) in Northern Hemisphere in summer of 1948-2005 are studied, indicating that they have an obvious interdecadal variation, especially in East Asian, North Africa and northern polar area. There are two abrupt processes for summer SLPs in the mid-late 1960's and 1970's. In terms of the interdecadal variation of the summer SLPs in Northern Hemisphere, the SLP anomalies firstly change in North European at the end of 1960's, then gradually moving southeastward. The positive anomalies of SLPs appear around area of Baikal Lake in the early of 1970's, then moving southward, in such a way that the positive center of SLP anomalies appears in East Asian in the middle of 1970's. Furthermore, SLP anomalies also change in Northwest Atlantic in the middle of 1960's, then moving gradually northward and southward, respectively. The positive anomalies strengthen the interdecadal variation intensity of SLPs in North European in the early of 1970's, meanwhile the SLP anomalies start to change in North Africa.