Abstract: This study introduces the correlation coefficient between Interval Valued Fuzzy Sets (IVFSs) and proposes an comprehensive assessment method of soil and water conservation of forest ecosystems based on the correlation coefficient, to solve the problem to assess the capability of soil and water conservation for some alternative places and determine the grades of the comprehensive evaluation in different regional conditions. A practical example of soil and water conservation in some alternative places of China is used for fuzzy comprehensive assessment problems as the demonstration of the applications and effectiveness of the proposed assessment method. The method proposed is significant on soil and water conservation in forest ecosystems and provide a new way to assess the capability of soil and water conservation.