Based on systemic method and theory，some elements influencing weight coefficient of data fusion capability evaluation index are analyzed. Mathematic models and methodological steps for weight coefficient of data fusion capability evaluation index determined by metasynthesis weight approaches are given out. Besides, the problem of sample data of index at high level is solved. Finally，Some comparative result of weight coefficient determined by three weight methods in data fusion capability evaluation test for a certain antiaircraft weapon are proposed according to examples analysis. Further it showed that metasynthesis weight approach is applied to determine weight coefficient of evaluation index for this system.