The Arctic climate system has been changing dramatically since the 21st century, of which the most important indicator is the unprecedented declining of the Arctic Sea Ice (ASI). The low ASI is not only closely related with Arctic amplification, but also plays a central role in the frequent cold Eurasian winters. In this paper, the seasonal feature of ASI and the current situation are introduced, and the possible reasons for the rapid shrinking of ASI are analyzed both dynamically and thermodynamically. Furthermore, the seasonal feature of the Arctic warming and its connection with ASI declining are discussed. The impact of the ASI declining on the atmospheric circulation in the northern winter hemisphere is summarized. The relationship between the ASI declining and increased occurrence of cold winters in Eurasia, as well as the potential mechanisms, are investigated. Lastly, this study proposes several issues that remain to be solved in this area.