Abstract: Currently, landraces account for 57.7% of the rice germplasm resources conserved in the National Crop Germplasm Bank of China. These landraces represent important genetic sources for exploring excellent germplasm and genes related to large panicles, multiple grains, large grains, and highly adaptable to different environments. Therefore, the identification and evaluation of major agronomic traits in rice landraces are crucial for rice breeding. In this study, 218 rice landraces collected from 12 provinces south of the Yangtze River in China were used as experimental materials. Twelve agronomic traits, including heading days, plant height, panicles per plant, and spikelets per panicle, were evaluated under two environments: Sanya of Hainan province and Huishui of Guizhou province. The results revealed significant phenotypic variations in these agronomic traits between the two environments. Heading days, plant height, panicle length, spikelets per panicle, and seed setting rate were significantly higher in Huishui, which has higher latitude and altitude, than in Sanya. In contrast, panicles per plant and flag leaf width were higher in Sanya than in Huishui. Thousand-grain weight, grain shape traits, and flag leaf width were the most stable across the two environments, followed by heading days, plant height, panicle length, seed setting rate, and flag leaf length; panicles per plant and spikelets per panicle were the least stable. Analysis of the coefficient of variation (CV) distribution for 12 agronomic traits among the 218 experimental materials revealed that the vast majorty of materials exhibited large CV for effective panicles per plant and spikelets per panicle, making these traits highly susceptible to the influence of different environments. In contrast, vast majority of materials showed small CV for thousand-grain weight, grain length-width ratio, grain length, and grain width, indicating these traits were not easily affected by different environments. For heading days, plant height, and seed setting rate, approximately half of the materials were environmentally sensitive, while the other half were insensitive. Panicle length and flag leaf length were relatively sensitive to environmental change for most materials, whereas flag leaf width was relatively insensitive. Indica landraces exhibited lower CV values for heading days and were generally more stable than japonica landraces. Indica landraces from the Middle and Lower Yangtze River Rice Region showed the highest stability. Compared with japonica landraces, indica landraces displayed earlier maturity, more panicles per plant, longer and more slender grains, longer flag leaves, higher seed setting rate, and higher thousand-grain weight. In contrast, japonica landraces had higher plant height, longer panicles, more grains per panicle, and wider grains. Landraces from the South China Rice Region and Southwest China Rice Region generally exhibited taller plant height, larger panicles, heavier grains, higher seed setting rate, longer grain length, and wider flag leaves, indicating higher yield potential. Cluster analysis showed the closest genetic relationship between landraces from the South China and Southwest China Rice Regions, followed by those between the Middle and Lower Yangtze River and East China Rice Regions. Based on stability in heading days, 20 elite landraces, such as Huangsigu, Dalongnian, Beizinuo, and Shoutianjian, were identified as having broad adaptability. Meanwhile, based on yield-related traits, 20 excellent landraces with high grain number, large grains, multiple panicles, or long grain shape were selected. These elite landraces combine wide adaptability with outstanding yield-related traits and represent valuable parental resources for rice breeding. Keywords: Different ecological environments; rice landraces; agronomic traits; stability; genetic relationship