In this study,by using daily data from the Department of Energy Reanalysis at the National Center for Environmental Prediction,dating from 1979 to 2015,we investigated the connection between Okhotsk blockings and mid-high latitude atmospheric intraseasonal oscillation(ISO) in the boreal winter.The results showed that the ISO perturbation over a key area of 60°-75°N,130°-160°E is the most greatly co-variated with Okhotsk blockings.The averaged geopotential height over this key area exhibits a statistically significant 10 to 30-day periodicity.By applying lead-lag composite analysis,it is revealed that the ISO perturbation associated with the Okhotsk blocking activity exhibits pronounced westward propagation.The perturbation initiates at about 140°W,triggered by intraseasonal wave energy accumulation.A geopotential tendency diagnosis reveals that the time change rate of the geopotential height over the key area is primarily attributed to the dynamic process.In addition,the results of a scale analysis show that the advection of mean vorticity by the ISO meridional flow plays a dominant role in the time change rate of the geopotential height during the occurrence and maintenance of the summertime Okhotsk blockings.