With the development of the third sector, social organizations have gradually become the core subject in social governance, with an increasingly important role in providing social services, solving social problems, promoting the development of social management, and building state-society relations. The Chinese context, however, has witnessed extended political ties between social organizations and the government. According to a report in 2013 in the South Reviews magazine, quite a portion of over 20 000 social organizations in a Chinese province had kept close ″ties″ with government departments. Therefore, an exploration into the impacts of these political ties on the effectiveness of social organizations will not only contribute to a deepened understanding of their behaviors, but also register a profound significance in facilitating economic and social transformations. Previous studies have discussed the relationship between governments and social organizations from the macro and meso levels of structures and institutional environments by applying theories of civil society and corporatism. Yet, as to how an institutional environment shapes behaviors of social organizations, and how social organizations cope with external environments, analysis and discussions made from the perspective of micro-mechanism can be rarely found. Our questionnaire survey of 254 social organizations has revealed that the political ties of social organizations generate a significant positive impact on organizational effectiveness, which is mediated by organizational autonomy. Further research shows that institutional support will moderate this intermediary relationship. Specifically, a higher level of institutional support will enhance the indirect effect of political ties on the effectiveness of an organization through organizational autonomy; similarly, a lower level of institutional support will weaken that effect. Compared to the previous studies, this study contributes to the extant literature in the following three aspects. First, the previous ones looked into state-society relations from the macro and meso levels yet overlooked questions of how social organizations behaved at the micro level and how institutional environments influenced behavior of social organizations. By trying to analyze the interactive mechanism between the state and society from the micro level with a focus on ″action strategies″ of Chinese social organizations, this study is a necessary supplement to the previous studies on discussing the ″controversy of structure″ from perspectives of state politics and power allocation. Second, this study provides a new perspective for researches on social organizations by introducing ″political ties″ in enterprise research into the researches of social organizations. In the past, the study of the relationship between social organizations and governments considered more of the formal relationship formed by property relations or administrative relations from the organizational perspective, keeping the informal social relationship between social organizations and governments out of their scope of research. This paper picks up the informal relationship between social organizations and governments caused by social networks as its research topic, trying to expand researches into this field. Third, this study has established the model of ″Political Ties — Organizational Autonomy — Organizational Effectiveness″ to clarify the relationship between political ties and organizational effectiveness by combing through the moderate mechanism of institutional support, which opens up the ″black-box″ between political ties and organizational effectiveness, and provides a basis for deepening the understanding of the development of Chinese social organizations. And more importantly, the results also provide theoretical guidance for the regulations over Chinese social organizations.