In this study seismic responses of dam-reservoir-foundation coupled system has been determined with inclined reservoir bed. The bed slope of the reservoir changes due to scouring or siltation and may affect the responses of the coupled system. In the present study, variation of hydrodynamic pressure adjacent to the gravity dam and stresses at heel of the dam has been observed for change of bed slope of the reservoir in anticlockwise and clockwise direction by applying seismic excitation including fluid-structure and soil-structure interaction. The stresses of foundation near heel of the dam have been observed for earthquake excitation. Geometry of the coupled system is discretized using finite element and dynamic analysis of the system carried by direct coupling approach. Significant changes have been observed in seismic responses of dam, reservoir and foundation for variation of reservoir bed slope.