If the morbidity appears in the discrete GM(1,1) model, it will lead to the instability of the model.Therefore, multiple and rotation transformation is used to solve the morbidity of discrete GM(1,1) model.It is founded that the causes of the morbidity of discrete GM (1,1) model are related to the ratio of the length and the angle with the accumulation vector and the vector with all the elements equal to 1.The matrix is regulated to a well-conditioned one by multiple and rotation transformation of vectors, which can completely solve the instability of the discrete GM(1,1) model.Numerical results show that vector transformation is an effective method for the morbidity problem of the discrete GM(1,1) model.