Understanding the spatial ecology of a species is essential for the species conservation. Reptiles are relatively understudied due to their secret lifestyle, despite of their important role in ecosystems. The Slender racer (Orientocoluber spinalis) is broadly distributed in Northeast Asia, but its observation frequency is low worldwide and there are few related ecological researches. Due to its rarity, O. spinalis is designated as a near-threatened species in the Republic of Korea, and as an endangered species in Mongolia and Russia. We sutdied the habitat characteristics and the home range of O. spinalis using the radio-telemetry on Oyeon Island (36.22°N, 126.08°E), Boryeong, Republic of Korea from 18 July 2021 to 9 August and from 4 September to 13 October. In eight successfully tracked O. spinalis, the mean daily moved distance was 26.1 m, and the mean home range was 1.66 ha by minimum convex polygon and 2.11 ha by Kernel 95%. The habitat types where the individuals were mostly observed were grasslands (56.0%) and followed by barelands (22.7%) and forests (17.7%). They most frequently used grasses (60.6%) and followed rocks (37.9%) as substrates. Considering the movement pattern and the core habitat, we suggest that O. spinalis uses grasslands adjacent to forests as its main habitat. Therefore, we suggest that the creation of grasslands adjacent to forests with shelters such as rocks would be more efficient than simply providing a large area or the conservation of O. spinalis habitat. This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2020R1I1A3051885).