Abstract:The tracks of tropical cyclones (TC) Matmo (1410) and Polly (9216) were very similar over Liao-dong Peninsula. However, the former caused only scattered rainstorms, but the latter produced large-scale rainstorms. Using CMA Tropical Cyclone Yearbook, FY-2D temperature of brightness blackbody (TBB) product (0.1°×0.1°), satellite observed TBB data issued by Japanese Meteorological Administration, hourly rainfall observations from Dalian’s automatic weather stations (AWSs), conventional observation and ERA-Interim reanalysis data （0.125°×0.125°）, the two TC cases that affected Liaodong Peninsula were compared and diagnosed. The results showed that (1) Polly and Matmo experienced extratropical transition when approaching westerly troughs. Frontogenesis zones were found in the lower layers of them. The western frontal zone had the cold frontal feature and the northern frontal zone had the warm frontal feature. Both of the precipitation over Liaodong Peninsula appeared in the northern frontogenesis processes. Meanwhile, the vertical wind shears were enhanced. But the characteristics of large-scale circulation of the two TCs were quite different. The cold air in the lower and middle troposphere invaded into Polly’s northwest side, the frontal zone slanted towards northwest with height, Polly produced heavy precipitation with a much longer time period due to abundant moisture supply from the low-level southeast jet. However, the frontal zone slanted towards northeast with height under the interaction between Matmo and the low level cold air being from the northeast of the typhoon. It met with a weaker rain rate with poor dynamic lifting condition and being cut-off with the low-level moisture jet. (2) The distributions of rainfall of Polly and Matmo showed clear asymmetric structures when impacting Liaodong Peninsula. The locations of heavy rain mainly occurred in the left along with the direction of the vertical wind shear. However, when the upper-level trough was located over different quadrant of TC, it suffered from a very different formation and strengthening of mesoscale cloud cluster.The convection activity of Polly was located at the north quadrant of typhoon inclining to southwest afterwards, but for Matmo, the convection activity only occurred in the northeast quadrant of typhoon. (3) Severe rainfall was closely related to the cold and warm advections in the typhoon circulation. The cold advection on the northwest side of Polly was strengthened, and Liaodong Peninsula was just controlled by the north of typhoon, possessing the cold and warm advections intersection in low-level circulation, strong low-level convergence, and deep and persistent vertical motion. However, there existed strong cold advection on the northeast side of Matmo, and Liaodong Peninsula was gradually under the west of typhoon, where the cold advection produced downward motion, dynamic lifting was reduced and the atmospheric stratification tended to be stable.