Abstract: In this paper, we discuss the robust H∞ control problem for a class of affine nonlinear systems with norm-bounded uncertainties in both free system and input matrices. We present a state feedback control design which stabilizes the plant and guarantees an H∞ norm bound constrain on disturbance attenuation for all admissible uncertainties. The robust Ha control problem is solved by finding a solution for Hamilton-Jacobi inequality, which is the nonlinear analogy of Riccati inequality appearring in study of H∞ control problem of linear system.