With the proliferation of the Internet of Things (IoT), various services are emerging with totally different features and requirements, which cannot be supported by the current fifth generation of mobile cellular networks (5G). The future sixth generation of mobile cellular networks (6G) is expected to have the capability to support new and unknown services with changing requirements. Hence, in addition to enhancing its capability by 10–100 times compared with 5G, 6G should also be intelligent and open to adapt to the ever-changing services in the IoT, which requires a convergence of Communication, Computing and Caching (3C). Based on the analysis of the requirements of new services for 6G, this paper identifies key enabling technologies for an intelligent and open 6G network, all featured with 3C convergence. These technologies cover fundamental and emerging topics, including 3C-based spectrum management, radio channel construction, delay-aware transmission, wireless distributed computing, and network self-evolution. From the detailed analysis of these 3C-based technologies presented in this paper, we can see that although they are promising to enable an intelligent and open 6G, more efforts are needed to realize the expected 6G network.