With the blended learning widespread in higher education, the research on the factors which can influence the students' engagement and their working mechanism has become more and more valuable. In this study, college students' perception on three aspects, i.e. their cognitive engagement and emotional engagement in two different activities, the activity features and teachers' roles, has been collected through both questionnaires and interviews. Repeated variance measurement, Pearson correlation analysis and General linear regression have been used to process the quantitative data. Thematic analysis has been used to process the qualitative data. The results show that the cognitive engagement and emotional engagement in Teacher's Q & A and Online discussion are significantly different (F[subscript CE] = 10.32**, [eng][superscript 2] = 0.07; F[subscript EE] = 29.60***, [eng][superscript 2] = 0.17). Students' emotional engagement and cognitive engagement in activities are affected by various task features and teacher's roles. Pedagogical implication and suggestions for further research have also been provided.