Objective To investigate the role of problem-based learning (PBL) in self-learning ability of medical students in extended-academic-year system. Methods Two hundred students of different grades in 8-year academic program were divided into control group （n=100） and test group （n=100）, and were asked to complete the Students Self-learning Scale. The Scale was composed of 40 items, and were classified into 16 first-order factors and 4 second-order factors, which were self-regulation, motivation, content and environment, and learning strategy. The items were designed in the form of multiple choice questions, and five-scale scoring method was used. Students in test group were also asked to complete 2 subjective choice questions about the subjective evaluation of PBL after the Scale. Results The scores of second-order factors of self-regulation, learning strategy and content and environment in test group were significantly higher than those in control group (P<0.01), while there was no significant difference in the score of factor of motivation (P>0.05). With respect to subjective choice questions, 70% of students in test group thought PBL played an important role in cultivation of self-learning ability, and 59% of students held the opinion that PBL was a good reform, which stimulated the self-learning ability. Conclusion PBL may promote the self-learning ability of medical students in extended-academic-year system, and stimulate the factors of self-regulation, learning strategy, and content and environment, while has no significant effect on the factor of motivation.