The Online Education Assistance Project (OEAP) is an online collaborative teaching project. This research took the OEAP as a case and used qualitative research methods to analyze the conditions of the OEAP as a professional learning community (PLC), the important factors affecting the development and construction of the OEAP, and the significance of developing and building a PLC. It was found that teachers' individual factors, working environment and students' academic conditions were all important factors affecting the sustainable development and construction of PLC. In addition, the development and construction of PLC based on the OEAP not only promoted student learning, teacher professional development and school construction, but also provided reference for promoting the sharing of high-quality educational resources and regional education balance.