According to the evaluation principle of dam system planning and the analytical hierarchy process (AHP),three hierarchies and nine indicators are selected as an evaluation system of dam system planning. Calculation method for each index in the evaluation system of dam system planning is obtained by analyses, weighted value of each index is determined,and finally a comprehensive index of dam system in small watershed is calculated.The computational results show that the greater the comprehensive index in small watershed, the better the economic,social and ecological benefits are.Therefore,the greatest comprehensive index may be selected as the best solution in the schemes for dam system planning in small watershed.The approach can be recommended for practical uses.