This dissertation investigates the nature of transnational advocacy networks and the impact of domestic structures on the development and political relations of such networks. Drawing upon the theoretical frameworks built by Margaret Keck, Katherine Sikkink and Sanjeev Khagram, I, though, challenge the conceptual bias embedded in this body of literature emphasizing contentious political relations between advocacy actors and targeted governments. I use the method of in-depth comparative case studies, and focus on two transnational advocacy networks in nature conservation and HIV/AIDS prevention in China to illustrate my three-fold argument: First, it is necessary to relax the theoretical bias in existing transnational advocacy literature, and recognize that the triangular relationship among the state, local society and international NSAs varies both over time and across issue areas. The two cases studied reveals a what I call the "double-mobilization" character of such networks. This Double-mobilization pattern emphasizes that international advocacy actors endeavor to engage, collaborate with, and advocate around the state, even as they establish connections and solidarity with local societal groups. I propose this double-mobilization concept to capture the gradual, consensual, and sustainable aspect of transnational activism. Second, it is not sufficient to use political regime type as the main causal variable to examine the emergence and evolvement of transnational activism and advocacy networks. Evidence from China has shown that the politics generated by international NSAs in a non-democratic country is complex, and despite strict macro-structures, transnational advocacy networks are emerging. Third, I argue that two domestic micro-level structures--decentralization within the state, and interconnections within existing civil society groups--strongly influence the political relations of transnational activism and networks. With decentralized environmental governance, and a strong and connected local environmentalist community, international NGOs have been able to generate, expand, and consolidate their mobilization networks in both governmental and societal domains in nature conservation. While transnational NGO linkages and networks are surfacing in HIV/AIDS preventions in China, both the scope and level of deepening of such networks are still limited.