This study aimed to explore how vocational high school students transfer knowledge through a problem-based learning (PBL) Internet platform. A PBL Internet platform was provided to 33 sophomore mechanical engineering students for a 6-week teaching experiment. A survey questionnaire, observation and interview were research instruments. The findings include: 1) factual, conceptual and process knowledge are the major types of knowledge and the sources of knowledge transfer (KT) include students, instructors and industries, but may be acquired differently depending on the level of problem-solving needs; 2) students' KT includes highly experienced tacit knowledge and more concrete explicit knowledge; 3) students' attitudes toward the six domains of using the PBL Internet platform all show positive significance, including the platform, the platform instructors, the platform mobility, online interaction, the PBL and the platform interface mechanism of students' perceptions; 4) the capability and the willingness for KT in instructors, industries and students all have some impact on the effectiveness of KT. (Contains 2 tables and 3 figures.)