The Internet of Things (IoT), as an important technical domain in the future, has received wide attention globally from different disciplines. The research output in this domain, therefore, grew rapidly in the past 10 years. This study deeply investigates the knowledge base and knowledge development trajectory of the domain since the IoT was proffered in 1999. By adopting basic statistical and keyword co-occurrence methods, the most influential countries, institutions, journals and scholars in the domain, as well as the division of core, hot keywords and subdomains, are investigated. By using the main path analysis method, a survey is conducted on the development trajectory of the domain on the basis of knowledge inheritance; the four core branches-industry, big data, cloud computing and IoT security; and the three application studies of industry, healthcare and smart city.