Abstract: Ultra-deep engineering is constrained by multiple factors such as high temperature and high pressure, complicated formations, ultra-long wellbore and acid fluids, resulting in all-round technical challenges for the safe and efficient operations. This paper focuses on the safe and efficient operations in ultra-deep well engineering, and summarizes the development overview and technical characteristics of ultra-deep well engineering. Next, research progresses at home and abroad as well as the latest research results of the authors’ team on several important theoretical and technical issues in ultra-deep well engineering are introduced, including well trajectory prediction and rapid drilling with hole deviation control, characteristic analysis and control technology of downhole drillstring vibration, prediction and control techniques of drilling limit, casing failure risk assessment and safety protection techniques. Finally, some suggestions are put forward on the innovative development of theory and techniques in ultra-deep well engineering. It is indicated that the overall development of ultra-deep well engineering theory and techniques have the typical characteristics of systematic, scientific, interdisciplinary and geology-engineering integration. It is recommended to strengthen the research on fundamental theoretical issues, key and core techniques, technological collaboration relationship, technological iteration modes, and interdisciplinary integration, in order to provide important supports for the continuous innovative development of theory and techniques in ultra-deep well engineering.