A new method for resolving nonproportionally damping matrix into proportional damping matrix and remainder dampng matrix and a new method for solving nonproportionally damped systems were proposed respectively.After introducing the perturbation method in to the nonproportional damping matrix and response vector, the nonproportionally damped system was reduced to a series of proportionally damped systems,which can be decoupled by using modal transformation. Based on this,an approximatelly analytical solution was obtined. The examples show that the solution obtained by this method agrees very well with that by the numerical method.