Abstract: In order to build the general and objective fusion image quality assessment method, the key technique of fusion image quality subjective assessment were presented such as assessment object, assessment condition, assessment index and data processing based on the analysis to image quality subjective assessment method. Two subjective assessment indexes were provided including target detectable ability and details resolvable ability according to two typical vision tasks of target detection and scene understanding. Furthermore, the correlation was investigated between the whole perceptual quality with target detectable ability and details resolvable ability respectively. Experiments were performed for 189 fusion images generated by 9 kinds of fusion algorithms fusing visible and infrared images under 3 kind different scenes. Statistical result showed that the high correlation between the whole perceptual quality with details resolvable ability compared with the low correlation to target detectable ability. However, the index of target detectable ability was still effective and could be used in the actually vision task.