In the Western setting，the grassroots NGO coalition plays a vital role in promoting the public expression of vulnerable communities.Grassroots NGO coalition has gradually become the leading actor of national policy advocacy by resources and scale of community members.How-ever，China's grassroots NGOs coalition face many restrictions regarding organizational resources and political opportunities structure.Firstly，the grassroots NGOs relatively lack professionalism，funding，and other critical organizational resources.Secondly，the grassroots NGOs themselves and their coalition have difficulty obtaining legal status and have no institutional channels for policy expression.This unfavorable situation requires them to innovate‘alternative’strategies for public expression.The article finds that the grassroots NGO coalition of vulnerable communities has built up the political legitimacy of advocacy action by absorbing powerful social and political elites.It has also cooperated with international NGO to make up for the lack of internal and external resources，which also can expand the social impact and public attention on policy advocacy.Then，the grassroots NGO coalition selects the existing institutional channel for individuals as an intermediary to contacting government officials，submitting policy proposals.Meanwhile，the grassroots NGO coalition adopts professional elites to build the professionalism and social legitimacy of proposals.National policy advocacy also expands the political opportunities structure of local advocacy by promoting local citizens and grassroots NGOs to conduct social surveys，providing policy templates，and communicating with daily virtual communities.The changing structure offers the possibility for continuous advocacy action.