With the development of the Internet, the mobile networks have also gradually led the traditional financial trade to the mobile commerce. One of the emerging e-commerce payments, called third-party payment, is growing through the expansion of application fields. It is worth to study the issue about which factor affects the development of third-party payment, and then an approach called Decision Making Trial and Evaluation Laboratory (DEMATEL) was used to analyze. Subsequently, the metrics were categorized into four quadrants by applying the cause-and-effect relationship diagram, and the metrics were further defined as key factors. Finally, we defined three key factors: real-time customer service, perceived ease of use, and customer participation. The results can serve as a reference for the future development of third-party payment service providers to formulate the strategies for the operational development and resource allocation.