Based on the existing 3P model, this paper constructed a new 3P model under the blended-project-based learning (BPBL) environment, used the course teaching data to verify this model, and revealed the potential factors that affect the learning process and learning outcomes. The results showed that the presage variables of academic motivation and course design positively affect the process variables of blended learning experience and learning engagement, respectively. The presage variable of academic motivation and the process variable of learning engagement positively affect the product variable of transferable skill development, respectively. In blended-project-based learning, it is necessary to enhance students' sense of experience and engagement by improving their academic motivation and optimizing course design, thereby promoting the development of students' transferable skills. This study has certain implications for optimizing blended-project-based teaching and promoting the development of students' team work ability, demonstration skills, management skills, and other transferable abilities.