The CO emission transfer at city level, especially across sectors of cities, has not yet been sufficiently quantified. This paper analyzes the embodied CO transfer across sectors of 13 cities in Jing-Jin-Ji region (Beijing-Tianjin-Hebei in China) combining multi-regional input-output analysis with complex network analysis. The results show that (1) most embodied CO transfers are concentrated in a few sectors and emission reduction effects on these sectors can be quickly extended to the entire embodied CO transfer network (ECTN). (2) The electricity and hot water production and supply sector in Beijing have the most embodied CO export partners and the strongest control over embodied CO transfer. The construction sector in Beijing has the most embodied CO import partners and greatest influence on the ECTN. (3) At city level, 90% of embodied CO transfers occur within the city, and the general direction of embodied CO transfer across cities is from resource-rich cities, Tangshan and Handan, to developed cities, Beijing and Tianjin. At sector level, the largest embodied CO transfer path is electricity and hot water production and supply → metallurgy → construction sector. (4) Embodied CO transfers of sectors in the same or adjacent cities are denser. Collection of sectors in Beijing and Tianjin is the densest embodied CO transfer community.