There have been a considerable number of accuracy indexes for surrogate models in references. However, most of these indexes are not capable of comparing surrogate models of different data types. In this paper, the drawbacks of the existing indexes were firstly discussed. Then a new index named "Mean Normalized Absolute Error (MNEA)" was introduced. Kriging models of 11 different types of aerodynamic parameters from a tactical missile model were built, with the adding-points design of experiment method and cross-validation verification methods. The effectiveness of MNEA was verified by comparing the MNEA value and the correlation plots of the example, which had proved that MNEA can be used to compare the accuracy of surrogate models of different data types.