Based on our previous work, introducing an extended Goldbart ansatz, all eigenvalues of the Hessian matrix in our three-dimensional spin glass model are obtained. It is found that the vanishing smallest eigenvalue λ3 has two solutions, which correspond to the Gabay-Toulouse (GT) upper and Almeida-Thouless (AT) lower critical lines respectively. Finally, the relation between our theory and other method is discussed.