Abstract: This paper deals with the stable isotopes of hydrogen and oxygen in rain water, river water and groundwater from Hainan Island of China. Water samples were collected in summer season of 1990. Results show: 1. The δD values of rain water samples from Hainan Island are much lower than δD values which were obtained by extrapolation from the distrbution tendency of δD values in rain water of the mainland China. The elope of the meteoric water line in Hainan Island is also much lower than that in the mainland China. 2. The δD and δ¹⁸O contentes of rain water, river water, and groundwater in eastern and southern areas are little higher than those in western and northern areas. The δD and δ¹⁸O contents in rain water, river water and groundwater decrease from low altitude to high altitude. The similarity of δD and δ¹⁸O of distribution of contentes in rain water, river water and groundwater, indicates the co-genesis of rain water, river water and groundwater in Hainan Island. 3. Data calculated by the isotope mixture equation showthat after each rain period the recharge of rain into streams is much higher than the recharge of rain into groudwater. This fact may lead to the shortage of groundwater resource in Hainan Island.