At the beginning of 2021, Vietnam encountered another wave of nCov epidemic, and students at University of Engineering and Technology, Vietnam National University, Hanoi, had to take online lessons instead of face-to-face ones. Many applications and websites were used to assist the distance learning and teaching process, and Google Classroom was one of them. This study focuses on the use of Google Classroom as an online teaching tool. The research was conducted during four weeks among 147 first-year students. The results were obtained from classroom observation and the analysis of students' assignments. The study points out that Google Classroom is an effective online teaching tool as it is free, easy to use, enables teachers to share materials, assign homework and create mini-tests for students.