To investigate into the influence of aeroengine assembly condition on the performance of finger seal, an analysis method about the dynamic performance of C/C composite finger seal considering assembly condition is proposed. Firstly, a distributed mass equivalent dynamic model of finger seal with a stack of finger elements is built according to the mechanical behavior between the finger seal and rotor. Secondly, the equivalent parameters are determined, such as equivalent mass, equivalent structural stiffness coefficient, contact stiffness coefficient, frictional force and rotor displacement excitation. Lastly, the dynamic performance of C/C composite finger seal is calculated by the dynamic model, including the leakage rate and the finger stick/rotor contact pressure. It is shown that, in the accordance with clearance fit, no clearance fit and interference fit, the leakage gap of finger stick and the rotor would be decreased, while the contact pressure would be increased. It is reflected that the leakage and wear are two contradictory performance indexes of finger seal. Therefore the structural stiffness of finger stick is changed by structure design under the certain assembly condition. That makes the leakage and wear to be all optimal.