During the COVID-19 pandemic, online learning has become an important and widely used form of education. Many studies have pointed out that interaction is key to online learning. The Interaction Hierarchy Theory categorizes interactions in remote teaching into three types: operational, informational, and conceptual. Operational interaction serves as the foundation for all types of interactions and refers to the interface interactions that learners engage in at the behavioral level through the use of media features and tools in online learning. However, should we simply encourage higher intensity operational interaction? Specifically, live teaching, as a form of remote teaching, has a higher sense of immediacy and synchronicity compared to asynchronous learning. Should we encourage and guide students to engage in more operational interaction during live teaching? How would it affect learners' informational and conceptual interactions? In this study, 137 students from 21 live classes were grouped according to class size and operational interaction intensity, and their levels of informational and conceptual interaction were explored. The results showed that the conceptual interaction intensity of learners in live teaching was higher than the informational interaction intensity, and operational interaction intensity and class size both had an impact on informational interaction, but a weaker impact on conceptual interaction. Operational interaction can affect conceptual interaction through informational interaction, especially through the mediation of student-resource informational interaction. The contribution of this study lies in verifying the establishment of the interaction hierarchy tower in the live teaching scene, that is, there are three different levels of interactive influence chains from operational interaction, informational interaction and conceptual interaction. Operational interaction and class size have a strong influence on information interaction directly and conceptual interaction indirectly. In online learning aiming at high-level interaction such as conceptual interaction, designers should not blindly promote operational interaction, but should pay attention to the promoting effect of operational interaction on informational interaction, and the operational interaction without effect on learners' informational interaction is invalid. In addition to enhancing operational interaction, controlling class size is also a way to facilitate informational interaction.