：In order to investigate the transient response problems of centrifugal impellers subjected to gas excitation in the flow fields, an algorithm to calculate the forced vibrations of impellers under non-cyclic aerodynamic forces is realized using the single-sector model. The cyclic symmetry of structure is considered in the programming. The unsteady guide vane/impeller interference with non-equal pitches is simulated by the time inclined method, and then the aerodynamic forces on blade surfaces are transferred from the flow mesh to the structural grid. Modal shapes of difference nodal diameters are solved by the FEAST solver, and then these data are expanded from the basic sector to all sectors. The load vectors are constructed according to the time differences of periodic exciting forces among the sectors. After that, the Newmark method is adopted to integrate the structural dynamic equations. Finally, the transient response analyses of a radial impeller under two rotational speeds are carried out. The displacement response results obtained from the single-sector model agree well with those from the integral model. The responses under two exciting frequencies near the potential resonance points both show almost divergent variation trends. All the results manifest the correctness of algorithm and its effectiveness to predict the resonance caused by gas excitation.