This study aims to systematically analyze the new characteristics, evolution trends, and causes of major extreme weather in China in the context of global climate change, and evaluate the current forecasting, early-warning, and defense capabilities of the country. Based on this, a systematic improvement strategy is proposed. By integrating existing observational data, research results, and operation practices, this study sorts out the changing patterns of extreme weather such as typhoons, heavy rain, severe convection, high temperature and drought, as well as low temperature, freezing rain, and blizzard. The results indicate that climate change is leading to significant alterations in the intensity, frequency, duration, and geographical distribution of extreme weather in China. The core driving mechanisms are the increase in atmospheric water-holding capacity caused by global warming and the large-scale circulation adjustment resulting from the Arctic amplification effect triggered by Arctic warming. The specific manifestations are as follows: the intensity of typhoons increases, their movement slows down, and their impact on the inland deepens. Although the total frequency of heavy rain has slightly decreased, its extremity, affected areas, and northward movement trend have intensified. Severe convective weather is more sudden and shows a more obvious trend of fragmentation. The number of compound events of high temperature and drought has increased. The harm caused by low temperature, freezing rain, and blizzard has increased each time. China's meteorological modernization level has significantly improved, and the defense work for extreme weather has made positive progress, including the establishment of a ground-air-space three-dimensional monitoring network, significant improvement in the level of independently developed numerical models and artificial intelligence models, and gradual improvement in the early warning system and information dissemination channels. However, there are still severe challenges in aspects such as the uniformity of observational data distribution, precise forecasting of extreme weather, and chain disaster defense. It is recommended to take practical actions in strengthening core technology research and development to enhance the country's disaster prevention and mitigation capabilities, implementing cross-departmental data sharing to build an intelligent collaborative early-warning platform, improving the progressive service and full-chain response mechanism to enhance the technological support capacity for resilient infrastructure, improving public participation, and strengthening the construction of the social security system. Meanwhile, it is necessary to carry out a systematic transformation from technological breakthrough to social empowerment to enhance China's capabilities to defense against extreme weather conditions.