The advancement of modern multimedia and internet education systems has enriched the presentation and dissemination methods of educational resources and changed people’s learning methods and behavior habits. Online learning has become a way of life and a hotspot of the times, and optimizing the quality of online education services has gradually become a common demand of society. IoT is the sense of relating all things to the Internet. It is another type of network that has been extended and expanded by accelerated improvements in network infrastructure. It has powerful communication, data storage, modification, and computing functions for related logic and data. From the perspective of online course construction, this paper proposes a research direction of IoT online courses based on multimedia technology. Firstly, a brief introduction to the theoretical overview of online courses is given, and then, an in-depth study of the IoT technology is carried out. Then, through the theoretical analysis of the online course mode, combined with the characteristics and functions of the IoT of multimedia technology, the design method of the online course system is proposed. Finally, a comparative experiment is conducted between the IoT online course of multimedia technology and the traditional online course. The experimental results show that the overall mean of the students’ two test scores under the IoT online course teaching of multimedia technology is 6.675 points higher than that under the traditional online course teaching. It shows that the teaching of IoT online courses based on multimedia technology is more conducive to improving students’ learning ability and level, thereby improving the quality of teaching.