An analytical method to solve the nonclassical damping system is presented. Real exact solutions of the free vibration and forced vibration of multidegreeoffreedom systems with nonproportional viscous damping are given respectively. In virtue of solving simple linear algebraic equations,the solutions of the free vibration in subcritical damping, entirely and partially degenerate damping may be obtained.For the forced vibration, the problem of solving the steadystate and transient vibration can be turned into solving the linear algebraic equations too. The examples show that the analytical solutions obtained by this method agree well with the solutions obtained by the numerical method.Thus,this method is very effective to analyze the non proportional damping system.