Abstract: It was tried to reveal the seasonal variation of water use pattern of Ficus tinctoria by a Hydrogen-oxygen stable isotope analysis of its stem xylem water and other potential water sources.The results indicated that the minimum soil water potential was-30.5kPa at 30cm deep in the dry hot season,while the maximum was -14.5kPa at 30cm deep in the foggy season.There was no variation in the soil water potential at 70cm in depth through all seasons.The soil water content was significantly higher in the rainy season than in the dry hot season and foggy season(P 0.001),but the difference of the soil water content between the foggy season and the dry hot season was not significant(P=0.64).Therefore,a seasonal variation of water use pattern did exist in different seasons.Rainwater and the water in the shallow soil were the main sources in the rainy season;in the foggy season,the main water source was the soil water(both in the shallow soil and the deep soil);and in the dry hot season,the main water source was the water in the shallow soil.