East Asian summer climate is controlled by a low pressure system centered over continental northern East Asia in the lower troposphere, which is named as the Northeast Asia low pressure (NEAL). Based on the NCEP-DOE, NCEP-NCAR, ERA-40, and ERA-Interim reanalysis data, we investigate the inter-decadal change of the summertime Northeast Asia Low-pressure system and discuss the possible physical mechanism associated with this change. Results show that NEAL experienced a significant decadal change in the early 1990s. The intensity of NEAL has decreased since 1991. Corresponding to the weakened NEAL, the tropospheric geopotential height field over Northeast Asia presents a barotropic-structure positive anomaly and the intensity of upper-tropospheric westerly jet to the south decreases. Based on results from the observational analysis and simulations of a linear baroclinic model, it is found that the surface warming around the Lake Baikal in the summer may be responsible for the weakening of the NEAL after the early 1990s.