Deep earth science in the 21st century has entered a new stage of development. The laws of deep earth science have not yet been explored. Deep engineering activities generally have a certain degree of blindness, inefficiency and uncertainty, and the endogenous dynamics of the Earth’s deep part, structural evolutionary laws, and disaster-causing mechanisms need to be further cognised. Therefore, this paper firstly defines deep earth science from the perspective of geoscience: the deep and ultra-deep layers of the earth are the research objects from the shallow earth to the deep, aiming at exploring the scientific mysteries of the earth’s different layers and different depths of the earth (deep and ultra-deep); clarifies the difference and connection between the deep earth science and the earth science: that is to say, the deep earth science is an extension of the known knowledge system of the earth science, and it is the national strategic science and technology direction to expand the scientific horizons, and to deepen the earth’s cognition. It is a national strategic scientific and technological direction to expand scientific vision and deepen earth knowledge, which is included in earth science; it defines the essence of deep and deep earth engineering science: that is, for the difficulties that the existing scientific laws and technologies of shallow engineering cannot be applied to deep engineering, it is necessary to explore the relevant scientific laws of deep engineering, break through the key basic scientific problems of deep engineering, and meet the demand for geo-disaster prevention and control of human beings in the activities of deep engineering, and then guide the safe, efficient, and green development of deep resources and effective utilization of the space of deep engineering; at the same time, it further clarifies the difference and connection between deep earth science and earth science. This article proposes the definition of deep earth engineering technology, which refers to the engineering implementation technology and equipment required by humans to utilize and develop the Earth, as well as the necessary theoretical and technical means to explore the laws of deep earth science and develop deep earth engineering. Finally, to promote the development of deep earth science, the research content and strategic planning of deep earth science, and the connotation of deep earth engineering technology, have been further clarified (geomechanics and disaster mechanism of deep-earth engineering, intelligent construction and efficient mining, intelligent construction of deep-earth tunnels and giant cavern groups, intelligent disaster prevention and control as well as healthy operation and maintenance of deep-earth engineering)
