This paper consists of following 3 parts:1. discusion on the method and conception of Potential Evapotranspiration.2. calculation and distribution of the Potential Evapotranspiration in China.3. some problems on the Potential Evapotranspiration studies.The first part discusses different methods of measuring the evapotranspiration and suggests to distinguish different conceptions of Potential Evapotranspiration according to the condition under which they are measured or calculated. Four conceptions are identified: Normal Potential Evapotranspiration (NPE) under the condition of unlimited water supply, complete vegetation cover and surrounded with uniform large area; Climatic Potential Evapotranspiration (CPE) under the condition of unlimited water supply but without uniform vegetation; Pseudo-Potential Evapotranspiration (PPE) under the condition of limited water supply; and Local Potential Evapotranspiration (LPE) in a small area with unlimited water supply and surrounded with large area of arid or semiarid condition.In the second part, the H. L. Penman’s formula for calculating the Potential Evapotranspiration is applied and the Map of mean year’s Potential Evapotranspiration in China has been drawn.The third part deals with the orientation of the Potential Evapotranspiration studies. Two suggestions are emphasized: to improve the measuring instruments and to increase comprehensive studies.