Abstract: Using the NCEP/NCAR daily reanalysis data from May to August during 1980－2004, this paper samples some reinforcement processes of 105°E and 125°E cross-equatorial flow according to a certain standard, then studies the variation features of cross-equatorial flow and its relevant circulation feature in the Southern and Northern Hemispheres. Results are shown as follows: Firstly, corresponding to the reinforcement process of cross-equatorial flow, there is always circulation adjustment in the tropical and subtropical zone on the south or north sides of the channel, and the adjustment mainly denotes the Australia cold air activity in the Southern Hemisphere or the variation of convergence zone in the Northern Hemisphere, which are the main influence factors of cross-equatorial flow. Secondly, the Northern Hemisphere convergence zone has a close connection with the east-west oscillation of the western Pacific subtropical high, and its distribution partly determines the impact of the Southern Hemisphere circulation and cross-equatorial flow on the extratropical circulation. Thirdly, due to the difference of circulation adjustment in the Southern and Northern Hemispheres, the 125°E cross-equatorial flow always has more notable reinforcement processes than the 105°E cross-equatorial flow.