Collaboration networks are a compilation of dynamic relationships among multiple stakeholders within and across organizations. A megaproject may involve hundreds of organizations that may be competing for a new subproject while collaborating on other subprojects. However, some organizations have competitive advantages to win more tenders than others, and the reasons for such emergence are not thoroughly investigated yet. This study analyzed the network-based bidding competitiveness and the evolution of collaboration networks by social network analysis (SNA) through a 6-year (2008–2013) case study of a zone development project in Wuxi, China, a total number of 1,897 construction projects. The constructed megaproject collaboration network consists of four key project stakeholders: owners, contractors, designers, and quality supervisors. The analytical results show that during the evolution of the collaboration network in China, contractors and designers who exhibit higher normalized degree centralities and larger K-core values are more likely to win a new project tendering competitively. At the same time, owners are primarily inclined to choose the “return” partners, especially designers, as collaborators for future projects. This study enriches the existing literature on the bidding competitiveness in megaprojects and helps us better understand the mechanism of collaboration and competition in megaprojects and provides effective and dynamic strategies to establish relational contracts in megaprojects.