Due to the COVID-19 outbreak, we have to take online classes this semester. During winter holiday, we tested four kinds of live broadcast tools, such as Teachermate, QQ group sharing screen, QQ group classroom and Tencent Classroom, and analyzed their features. According to the characteristics of the course I teach, The microbial world, which is a core general education course with more than 100 students, I finally select Tencent Classroom as live broadcast tool, combining with Teachermate platform. This attempt had achieved good effect and provide a good glimpse into online course practice.