Abstract: A direct method for actual evapotranspiration (AET) measurement is presented,that is,the compensatory lysimeter method with three cylinders.By using this method,the evapotranspiration loss over water surface and aquatic macrophytes can be measured directly without destroying reed's living conditions.Experimental test was carried out in Zhalong wetland from 2004 to 2005 (during reed growing time in the middle of May-Oct.).The primary analysis results are as follows: (1) the average AET over reed belt of the two years is 812.1 mm and the average evaporation over water surface (E_w) is 433.9 mm; (2) the AET of reed belt reaches its maximum in June or July every year,while the maximum of E_w appears in May;and (3) the ratio of AET to E_w varies markedly in different months,and the average ratio in reed growing season is 1.87.By the observed data,a multi-regression equation of AET for Zhalong reed belt is established.It can serve as a useful tool for water resource planning and management of wetland.