It is difficult to select an appropriate evaluation index for current image fusion. In order to solve the problem, a synthesis evaluation index is proposed based on the correlation between subjective and objective evaluations. First, a variety of fusion results are evaluated subjectively from the edge of clarity, natural sense, in-formation and comprehensive evaluation, respectively. Secondly, 14 commonly objective indexes are used to evaluate the fusion results. Then, the subjective and objective results are normalized, and the Spearman correla-tion coefficient is used to analyze the correlation between the four subjective evaluations and each objective evaluation. Finally, according to the correlation, a comprehensive index is constructed through 14 objective in-dexes in 4 aspects. The experimental results show that the synthesis index is more relevant to subjective evalua-tion than the individual evaluation index and any other comprehensive indexes.