Abstract: In view of the dilemma of modernity caused by political decline,this paper studies Arendt's critical thoughts on the social sphere and makes an important supplement and improvement to the negative political consequences of the rise of the social sphere. Through a systematic study of the political hazards in the social sphere,this paper finds that Arendt's division of private sphere,social sphere and public sphere is not only an important framework for her criticism of modernity,but also an important theoretical tool for us to understand political modernity. The invasion of the social sphere into the political sphere brings the inevitability of domestic management in the private sphere into the free political sphere,which then leads to the rise of bourgeois,the decline of citizens and the decline of politics in human activities. In the face of the erosion of politics and people caused by the social sphere,it is necessary for us to re-examine the positive significance of public politics to the realization of the meaning of life.