Abstract: Biological invasions, as an important component of global change, have caused enormous ecological, economic and evolutionary impacts worldwide, posing a serious threat to the biodiversity conservation. The bluegill sunfish (Lepomis macrochirus), a quintessential exotic fish, has successfully established itself in some of China’s natural waters. Despite its presence, there is a notable absence of studies or reports on the life history characteristics and adaptations of bluegill sunfish populations in China. In this study, we systematically collected a total of 3484 samples of bluegill sunfish monthly from March 2021 to January 2023, focusing on the population in Qiandaohu Lake. We examined various life history traits, including age, growth, reproduction, and mortality, as well as bluegill sunfish adaptations. The results showed that the mean body length of bluegill sunfish was (88±0.6) mm, with a mean body weight of (30.42±0.53) g. The age structure displayed simplicity, predominantly featuring younger individuals aged 1—2 years (83.97%). The body length-weight relationship was obtained by fitting a power function equation as BW=1×10^–5SL 3.1543 (N=3484, R²=0.97). In addition, sexual dimorphism was evident in Qiandaohu Lake bluegill sunfish, with a breeding season spanning from April to September. Noteworthy reproductive characteristics included an absolute fecundity of (11405±921) grains/tail, a relative fecundity of (282±14) grains/g, and an average egg diameter of (0.74±0.003) mm. Natural mortality was estimated at 1.05/year using the empirical formula proposed by Pauly. The fishing (F) and total mortality (Z) coefficients, along with the exploitation rate (E) were estimated at 2.53/year, 3.58/year and 0.14, respectively, using the length-converted catch curve method. In summary, the population of bluegill sunfish in Qiandaohu Lake showed characteristics typical of an r-strategistis, with an overall increasing population size. This poses the potential risk of further expansion, destabilizing the ecosystem of Qiandaohu Lake, necessitating urgent management and control measures. The study identified key adaptive mechanisms contributing to the successful invasion of Qiandaohu Lake by bluegill sunfish, including alterations in reproductive timing and early growth rates. The results fill crucial gaps in basic information regarding the population growth, age structure and reproductive characteristics of bluegill sunfish in China. They shed light on the adaptive mechanisms underlying their successful invasionand provide an important theoretical foundation for preventing and controlling bluegill sunfish invasion in China.