Abstract: Based on the situation of the Baiyangdian Wetland in the extremely dry year  three water supplement schemes, i.e. minmimal water level scheme, appropriate ecological water level scheme and no water supplement scheme, were designed  to explore and calculate variations of various ecological service functions of the wetland as affected by water supplement , and economic values of the variations were assessed using the market value method, analogue method and shadow project method, and hence values of the ecological benefits of water supplement were worked out. Results show that according to the minimal water level scheme and the appropriate water level scheme, 12610×10⁴  and 26819×10⁴ m³ of water should be supplemented, respectively, and 57036×10⁴ and 135646×10⁴ Yuan (RMB) of ecological benefits would be created, respectively, in anticipation, including the indirect use value of 52255×10⁴ and 124244×10⁴ Yuan, respectively, which is 10.93 times and 10.90 times  of the direct use value, respectively.The ecological benefit per unit water supplemented to the Baiyangdian wetland of the two schemes is 4.5 and 5.1 Yuan•m^-3,respectively. It is quite obvious that the ecological benefits of the two schemes for water supplement to the Baiyangdian wetland are both very significant.

Key words: extremely dry year, water supplement, ecological benefit, assessment, Baiyangdian wetland