A comprehensive vibration analysis method for coupled rotor/fuselage system with flexible fuselage modeling is presented. Rotor loads are calculated by unsteady Euler/N-S equations and quasi-steady aerodynamics, the detailed 3-D finite element model of the fuselage is built by CSD software, nonlinear beam elements with 15 degrees of freedom are used for the rotor dynamics, and the coupled equations are solved by loose coupling method with trim. The fuselage vibration response of a two-bladed teetering rotor in hover has been investigated, and the results agree very well with the experiment data. Then the influences of flight speed and fuselage flexible on airframe dynamic response have been studied, the results showed that the vibration level increased with the flight speed in low and high speed flight states, and keeps invariant in the intermediate state.