Abstract: To improve the analysis and forecast of tropical cyclone (TC) wind circle, the asymmetric characteristics and causes of wind circle maximum radii of 55.6 km/h, 92.6 km/h and 118.5 km/h for TCs at their maximum intensity during 30 June 2015 to 31 December 2020 are studied using the TC data released by the National Meteorological Centre (NMC) and data extracted from ERA5 reanalysis. Statistical results show that the 55.6 km/h wind circle radius of TC is the most asymmetric, followed by the 92.6 km/h and 118.5 km/h wind circle radii. The 55.6 km/h, 92.6 km/h and 118.5 km/h wind circle maximum radii of TC with asymmetric distribution are mostly located at the north east (NE), southeast (SE) and northwest (NW) quadrants. The 55.6 km/h and 118.5 km/h wind circle maximum radii of the same TC are roughly located at the same quadrant. Single quadrant distribution TCs and multi-quadrant distribution TCs of 55.6 km/h wind circle are divided into four types according to quadrant distribution. By analyzing the generation season, surface wind and the causes of asymmetric distribution of TC with single quadrant distribution of 55.6 km/h wind circle, it is found that the generation of these four types of TC have obvious seasonal characteristics. The surface wind in different quadrants of TC shows asymmetric characteristic. The asymmetric distribution of wind circle is closely related to the asymmetry of potential height gradient in different quadrants caused by the interactions between TC and other weather systems, including the Western Pacific Subtropical High, the southwesterly air flow and surface cold high pressure, etc.