Abstract: Bigeye tuna Thunnuns Obesus is one of key species caught by Chinese tuna longline fleets. Its spatial distribution in relation to environmental factors is highlighted by international organizations and researchers. The aim of this study is to present the analysis of correlation between hooking rates of bigeye tuna longline and environmental factors in the Indian Ocean. Three environmental variables including temperature, temperature difference and dissolved oxygen difference are used to fit habitat suitability model in order to explain the distribution pattern of bigeye tuna in the Indian Ocean. Function expressions of hooking rates and environmental factors are estimated by quantile regression. Data predicted by optimum upper boundary quantile curves are fitted to the habitat suitability model to display quarterly distribution of bigeye tuna via visualization of Surfer 8.0. The optimum upper boundary quantile curves for temperature (T)-hooking rate (HR), temperature difference (dT)-HR and dissolved oxygen difference (dO)-HR are in the following , and , respectively. Habitat suitability index is above 0.9 within 10°N~10°S, 0.8~0.9 in the north of 10°N and within 10°S~15°S, 0.7~0.8 within 15°S~40°S, and below 0.6 in the south of 40°S. However, a mass of waters occurs seasonally within 50°E~90°E,15°S~25°S where habitat suitability index is less than 0.7. The habitat suitability model indicates the reliable results and could be improved by integrating more interactive variables. It is proved in this study that quantile regression is a useful way to investigate correlation between organism and limiting ecological factors. Key words：Thunnus obesus; quantile regression; habitat suitability index (HSI); Indian Ocean