Abstract: This paper points out that the sysstem of equations of grey model(GM model)has very serious morbidity problem We discuss the reasons why GM model has morbidity problem:1)Matrices are composed of accumulating numbers which have very large scalar difference among them;2)Degeneration in some grey model makes very large scalar difference among elements of matrices;3)The way to build matrices in grey model let us hardly reduce morbidity of the system of equations A widely referrenced example is analyiedin this paper At the end,we suggest that it must be careful to use grey model.

Key words: grey model, condition number, norm, illed system of equations, illed matrix, morbidity, perturbation analysis