Abstract: To study the characteristics of fractionation of hydrogen and oxygen isotopes in evaporating water in Hengshui, a typical region of the North China Plain, two sets of outdoor water evaporation experiments with different salinities were conducted under local meteorological conditions. Water was collected from deep fresh water (TDS=0.61 g/L) and shallow saline water (TDS=7.97g/L), respectively. The experimental results showed an exponential relationship between δD and δ¹⁸O in residual water and f (the volume ratio between the residual water and the initial water), which was in agreement with Rayleigh fractionation model results. The slopes between δD and δ¹⁸O in the residual surface water were 4.78 and 4.69 for the fresh water and saline water, respectively. It was also shown that the average degrees of enrichment of the hydrogen isotope D were 4.82 and 4.76 times those of the oxygen isotope¹⁸O in the fresh water and saline water, respectively. The ratios between the δD and δ¹⁸O variations of the residual surface water and the evaporation were 2.68‰/cm and 0.56‰/cm, respectively, for the fresh water; and were 2.78‰/cm and 0.61‰/cm for the saline water during the experiment period. Nevertheless, the ratios at different evaporating times had no significant correlations with each other. Isotopic statification was rarely observed in different water layers due to the diffusion effect of water molecules. Moreover, the salt effect on the stable isotopic fractionation during the pan evaporation experiment under the typical climatic conditions was negligible, probably due to the low salt concentration in the saline water.