Contents I. Introduction
Since the beginning of 2020, novel coronavirus has been plaguing the world frequently. Universities in epidemic-affected cities have been forced to “switch offline to online” as an emergency measure for education. Online teaching has changed from a “supporting role” to a leading role, becoming the new normal of current popular teaching. After the Ministry of Education put forward the instruction of “ceaselessly teaching, ceaselessly teaching, ceaselessly teaching”, all parts of the country responded one after another, in the nationwide fight against “epidemic” and home prevention “epidemic”, the large-scale application of online teaching, education seems to have entered the new era of “Internet plus” overnight. Online teaching is not a new term, but the large-scale application is the first case, as a new educational concept, how to design the teaching content? How does online teaching unfold? How to innovate teaching model? How to make good use of the platform and fully release the charm of “cloud” has become a hot topic in current educational theory research.” Online Learning” [1]–[3] Online Teaching, also known as Online Education, or e-learning, or distance Education, Online Learning, is a web-based Education or Learning mode, taking the network as the medium, using Online, using Tencent Classroom, we chat group, Rain classroom and other Teaching platforms, Realize the two-way interaction between teachers and students, the same screen resonance, effectively solve the problem of remote interconnection and distance teaching. Online teaching changes the space, but does not change the content. As the core of teaching activities, teaching content is all the knowledge passed by teachers to students, the center of realizing students' thinking shaping and ability generation, and the key to represent the quality and connotation of teaching. “If the foundation is not solid, the earth shakes”, online teaching without the support of high-quality content will inevitably go to the virtual. The teaching content determines the theme of online teaching, answers the questions of what teachers teach and what students learn, and solves the problems of pertinence, effectiveness and applicability of teaching. The form of teaching determines the way of online teaching, answers the questions of how teachers teach and how students learn, and solves the problems of interesting, innovative and methodological teaching. The unity of teaching and learning and the transformation of knowledge and practice can be realized only when the relationship between teaching content and teaching form is well handled and network resources, new media and teaching methods are integrated in knowledge reconstruction, module recombination and system reconstruction.
