The Rayleigh-Benard flow is one of typical models for studying the patterns and nonlinear dynamics of nonequilibrium convection.By using a two-dimensional numerical simulation of the fully hydrodynamics equations,Rayleigh-Benard convection under gravity modulation in a rectangular channel was studied Further,pattern formations and nonlinear characteristics were discussed.The results indicated that the change period of convection characteristic parameters depend on the cycle of gravity modulation.