The online mathematics teaching in primary schools under the background of COVID-19 epidemic is an important measure to implement the policy requirements of the Ministry of Education of "suspending classes without stopping teaching, and closing classes without stopping school". When adopting online teaching in primary school mathematics through network resources, it is not only to follow the development of the era of science and technology education, but also a science and technology park to cultivate teachers and students' innovative learning. Starting from the online teaching practice of primary school mathematics during the COVID-19 epidemic prevention and control period, this paper proposes the common problems existing in the online teaching of primary school mathematics. Finally, from the three aspects of teaching platform, teachers and students, we discuss the optimization strategy of online teaching in primary school mathematics, so as to better develop online teaching in the future, and better serve the teachers and students.