Network effect is the core strength of platform growth and the key to operation of platform institutions. Network effect refers to the improvement of utility and overall network performance obtained by platform network actors from optimizing network features, which is reflected in the utility of actors at the node level and the performance improvement at the overall network level. Network effects are not only related to scale, but also to other characteristic elements of network structure and functional dimensions. Based on the theoretical analysis framework of network effect influencing factors by Afuah, Turrinia, and others, three different types of internationally renowned open digital academic innovation platforms DOAJ, arXiv, and ORCID are selected for multi case exploratory research to analyze the influencing factors of their network effects and construct a theoretical analysis framework for the influencing factors of network effects on open digital academic innovation platforms. The research results indicate that network structure characteristics and network function characteristics are the main influencing factors of the network effect of digital academic innovation platforms. The characteristics of network structure refer to the relative features of the number, roles, positions, and relationships of actors. Among the characteristics of network structure, network size, network heterogeneity, network density, and network centrality are the main factors affecting the network effect of digital academic innovation platforms. The network functional characteristics refer to the role of the platform’s own nodes in the entire network, that is, the abilities and measures demonstrated by the creators and managers of the network in achieving network goals. For digital academic journal innovation platforms, network relationship capability and technological innovation level are the main factors affecting their network effects. Based on this, a theoretical framework for the influencing factors of the network effect of digital academic journal innovation platforms has been constructed, and countermeasures and suggestions have been proposed to stimulate the network effect of China’s open digital academic innovation platforms and promote their rapid growth.