Abstract: Abstract: At present, there have been no definite ways and applicable decision-making methods on the optimization of evaluation indexes, especially on the dilemma of the subjectification and non-systematization of the index selections in the ecological environment evaluation researches. Based on the index multi-information fusion, an optimized thought and a decision-making method has been put forward in this research. After collecting the three categories of feature information of index sensitivity, equilibrium degree and independence, the method of orthogonal experiment was used to calculate the index sensitivity in purpose of expressing the dynamic characteristics of indexes. The index equilibrium degree with the help of the definition of Gini coefficient in mathematical economics was calculated to select the simplest indexes that cover the most properties of the evaluation object. The independence of the indexes by means of index correlation analysis was determined to exclude some indexes with high degree of association. After that, DS (Dempster Shafer) evidence theory was adopted for the information fusion. The mentioned three index features can be regarded as three evidences, with the integration of the basic trust distribution function value. The index credibility jointly supported by the three evidences and optimized from the complicated and large index library according to the sequence results of the credibility. This research took the Jinghuiqu Irrigation District as the researching object. To understand connotation of ecological environment in irrigated district from perspective of system, the ecological environment concept model of the irrigation district was constructed to express driving factors of ecological environment in irrigated district, information carrier and representation state. The directed line segment was used to describe interaction and influence relation between different carriers, and the information expressed by this model was sorted. The factor layer was defined as “resources in the irrigation district”, and 31 indexes gradually determined. The ecological environmental evaluation index library of the irrigation district was primarily constructed. The DS evidence theory was used to realize the multi-source information fusion of the basic trust distribution function value of the three evidences. Two fusion thoughts were set: ①index entire fusion, ②separately remove the indexes of lower basic trust distribution function values under the three evidences, and then carry out fusion to the left indexes. The sequence of credibility of the index feature information was carried out after fusion from high to low, and the calculation results by the above two thoughts were compared and analyzed . The results showed that: the calculation under the thought ②would remove some indexes with relatively high credibility in advance, such as degree of acid and alkali, air relative humidity indicator. According to the thought ①, results for indexes credibility were ranked as follows: multiple cropping index > groundwater depth > solid erosion modulus > development and utilization rate of surface water resources > intensity of pesticide application > biodiversity index > vegetation coverage > intensity of chemical fertilizer>underwater mineralization>times of the heavy metal content of soil exceeding the background values > species richness > air relative humidity > overgrazing index > drought index > salinization index > drainage engineering coverage > rate of channel lining > biomass > urbanization rate > standard sewage discharge rate > surface water NH3-N concentration > utilization coefficient of irrigation water > percentage of impervious area > density distribution of wells > surface engineering of water supply capacity. Indexes with relatively high credibility could be selected as main indexes for research on ecological environment evaluation in irrigated area, which provided new thought and policy as well as method with optimized indexes for research on ecological environment evaluation in irrigated district as well as evaluation research in other fields.