This article focuses on analyzing and evaluating students' activities in blended learning to help teachers and educational institution leaders have timely interventions and adjustments to support learners to improve their learning efficiency. The author proposes relevant criteria for monitoring and evaluation based on three aspects including attitudes, technology skills, and learning effectiveness in the online phase of Blended learning. Base on the survey results, four important criteria were given to improve the effectiveness of Blended learning teaching, including (1) To encourage students to spend more time on learning
(2) To support students who have difficulties with technology skills
(3) To provide learning equipment and information technology infrastructure so students in need could borrow and study in specific areas
(4) To provide adjustments in assessment suitable for Blended learning.