Hydrangea luteovenosa is found only in Korea and Japan, but it is rare on the Korean peninsula, growing only in Jeju Island. There is limited information regarding their exact population size, distribution and growing conditions on Jeju Island. Therefore, this study aims to understand the ecological characteristics of their habitat and develop an in-situ conservation strategy by conducting complete enumeration and vegetation surveys of the H. luteovenosa population on Jeju Island. A total of 1,077 individuals were found at 34 sites along the upper reaches of the Seojungcheon River in Seogwipo City. They were distributed vertically between 433-636 meters and horizontally over approximately 3.5 kilometers. In particular, 65% of the total population was concentrated in an area of 2 hectares at an altitude of 550 meters above sea level. The habitat is a rocky area and steep slope on the edge of a valley, characterised by shallow soil depth and unstable site conditions due to periodic physical disturbance from flowing water. The vegetation climate zone of the population is located in the coldest upper part of the warm temperate evergreen broad-leaved forest zone bordering the cool temperate deciduous broad-leaved forest zone. Considering the high vegetative reproductive capacity and distributional characteristics of H. luteovenosa, it was determined that flooding and physical disturbance of the Mt. Halla dry stream act as opportunities for distributional expansion rather than threats. However, the small population, narrow and limited range and low genetic diversity due to vegetative reproduction were expected to make it vulnerable to threats such as artificial damage or rapid climate change. Therefore, the in-situ conservation strategy for H. luteovenosa is as follows: (1) the area with dense distribution should be designated as a priority conservation area and intensive management measures should be established, and (2) an ex-situ propagation and conservation strategy related to environmental adaptation should be developed. In particular, (3) since the distribution of the Jeju population is closely related to the climate and vegetation zones of Mt. Halla, it should be considered as a suitable target species for long-term monitoring of distribution changes expansion and contraction due to climate change.