Abstract: With the basic equation on non-conservative analytical mechanics with damping settled, according to the corresponding relations between generalized forces and generalized displacem-ents, the basic equations are multiplied by corresponding virtual quantities, integrated and then added algebraically. Considering that systems are non-conservative, the quasi-variational principle and the generalized quasi-variational principle of non-conservative analytical mechanics are established. Finally, based on quasi-Hamiltonian principle, an example on non-conservative systems of the two degree of freedom with damping is studied.