Blended learning is a learning style that combines a portion of learning materials and learning activities through an online learning platform. By studying the characteristics of online learning behaviors of freshmen in blended learning, we can further help them to better carry out their undergraduate study life. Through the study of online learning behavior characteristics of freshmen participating in blended learning, this article finds that: (1) Learners with siblings are more engaged in online learning behaviors than those without siblings, and the difference in forum participation is most significant. (2) Using K-means clustering analysis, learners can be classified into four categories based on their online learning characteristics learners: Comprehensive learners, Performance-oriented learners, Social learners and Task-oriented learners. (3) Learners with higher level of engagement in online learning are more likely to achieve better grades.