A new method based on data fusion about comprehensive evaluating of central air conditioning system was put forward, according to the analysis of existed evaluating index system at home and abroad of the central air-conditioning system. Five indexes of the central air- conditioning system were classified into income and payment. The ratio of income and payment was used as the new evaluating index. The method and formulas of data fusion about central air-conditioning system were given. Scoring criteria of theses evaluation indexes were also set up so that the parameter could be calculated. Three examples of central air conditioning system proved the simplification,feasibility and veracity about this new method.