Circular economy system is an open complex giant system. The integral characteristics of the system were discussed from the aspects of openness, highdimensional, complexity, massiveness, and emergence. The frame structure of the system was analyzed from various view points of systems of production, logistics, consumption, capacity support, social life, and artificial ecology. In micro, medium, macro and superscale ecological domains, the timespace structure of the system was discussed. The circular economy operation patterns were explored with the perspective of industrial enterprises, industrial clusters, agricultural industries, families and society. The integrated theories of circular economy were developed based on integrated idea, integrated foundation, integrated system and integrated innovation. The integrated technologies of circular economy were constructed by developing integrated methods, establishing integrated models and building integrated platforms. According to the 5 typical operation patterns, the integrated technologies were applied to realize the integrated engineering of circular economy.