The COVID-19 pandemic has had a serious impact on education at all levels and types, and the education system, including colleges and universities, has been forced to respond by a sudden shift to online teaching. Successful online teaching requires careful thinking, planning, and technical and human support from teachers. Based on the reflection on the offline classroom teaching of theoretical mechanics for many years and the online teaching practice of first half of 2020, the author summarizes effective strategies for implementing online teaching of theoretical mechanics. We prepared the theoretical mechanical lessons through a "student-centered" approach, such as preparing teaching materials, students and teaching methods. These teaching strategies include (i) Adopting live-stream teaching as the main teaching method, (ii) Applying electronic blackboard to online deductions, (iii) Linking theory to practice for better understanding of knowledge, (iv) Integrating curriculum content in ideological and moral education, (v) Conducting formative assessment to supervise and motivate online learning. The implementation of these online teaching strategies has effectively promoted the development of students' independent learning ability.