Objective:To retrospectively construct competency-based portfolios for medical students to analyze the factors influencing competency self-assessment, and to explore an approach to efficient portfolio construction.Methods:The participants were randomly selected among medical graduates of 2015 in Shantou University Medical College. Through records collection and an online questionnaire survey, portfolios were built for the participants based on their development data during eight years from college entrance, college education, to post-graduation medical education. The correlation between variables was determined using Kendall's tau-b correlation coefficients. The inter-group differences were analyzed using the Mann-Whitney U test. Results:A total of 126 usable questionnaires for effective developmental portfolios were collected. There were a total of 208 indicators collected, including 79 questionnaire indicators (including 36 for competency self-assessment). The reliability coefficient (Cronbach's α) of the questionnaire was 0.984. The factors related to competency self-assessment were identified. Conclusion:This study provides a basis for the implementation of portfolio assessment, which can promote students' self-assessment and competency development. Optimizing the indicator system, building an online platform, increasing participants' participation motivation, and emphasizing self-reflection and feedback will help improve the efficiency of developmental portfolio construction and its performance.