This research utilized blog as a tool to explore the impact of web-based learning portfolios on knowledge management. The participants were 88 students who major in Multimedia and Games Science Department from one Technology University in Taipei. Excluding the first preparation conditions (such as academic performance throughout the semester and a pre-test of knowledge management), we conducted an experimental design and used Multivariate Analysis of Covariance (MANCOVA) to understand the differences in KM between the experimental group (45 students) and control group(43 students), and then used t-test to examine the difference between pre-test and post-test of experimental group. The results showed that pre-test and post-test of experimental group had significant differences in five levels and overall knowledge management. Besides, the experimental group and control group also had significant differences in knowledge sharing, knowledge innovation, knowledge acquisition, knowledge application, knowledge accumulation and overall knowledge management. Hence, this research confirmed that web-based learning portfolios can help learners to perform knowledge management.