Identification of land use conflicts (LUCs) from the perspective of ecological security is essential for ensuring regional ecological security. Coastal zones in China experience complex management challenges related to increasing demands of ecological protection and economic development, similar to other coastal countries throughout the world. In this study, we established an index system for evaluating the ecological security importance from two perspectives: ecological sensitivity and importance of ecosystem service function. We then used this index system to delimit ecological security space and identify actual LUCs in China's coastal zones in 2018. In addition, we discussed the situation of LUCs in transitional zones of the coastal zones from a horizontal perspective. Results indicated prominent spatio–temporal mismatches among cultivated land, construction land, and the ecological spatial layout in coastal zones. In the ecological space, the area of cultivated land conflict zone was 12.60%, whereas that of the construction land conflict zone was 10.26%. LUCs existed in all coastal provinces. Overall, significant regional differences were observed in the distribution of LUCs, with near-land side and southern region showing higher distributions than the near-sea side and northern region, respectively. Meanwhile, the cultivated land conflict zone generally radiated outward with the construction land conflict zone as the ‘source’. The findings of this study can provide insights for decision-makers into the location of cultivated land and construction land, which are most likely to occupy ecologically important spaces.