Grey Model (GM) based on grey system theory has already been established as a prediction model in 1982. At present, it has been applied to many fields. However, in the traditional GM, the calculation methods of derivative value d(superscript n) x/dt(superscript n) and background value z are obtained by the analysis of observed white value. Therefore, it influenced the calculation of coefficient â and the prediction accuracy of the traditional GM is unsatisfied. Especially, the prediction accuracy falls in case of the multi-variable or multi-dimensional greatly. In this paper, a new calculation method of derivative value d(superscript n) x/dt(superscript n) and background value z is proposed according to cubic spline function and Taylor approximation method and it is analyzed by grey interval analysis. We obtain the new calculation method of coefficient â by the proposal GM, and this new model is defined as T-3spGM. We present two specific examples; the prediction accuracy of proposal model is verified. As the results, we report that the prediction accuracy of the proposal new model was raised greatly.