Utilizing the Littlejohn``s procedure of the Hamiltonian formulation, the nonlinear gyrokinetic equation is obtained for the low frequency and electrostatic problem. This equation generalizes the work of Dubin et al. to the general plasma equilibrium case. The general geometry effects are of first order and linear corrections while Dubin et al. calculate up to the second order of nonlinear corrections in the straight magnetic field. The phase space volume preserving property and energy conservation are discussed.