The control of amplitude of limit cycle emerging from the Hopf bifurcation in Langford system under a nonlinear feedback controller is investigate in this paper. Explicit nonlinear control formulae and amplitude approximations in terms of control gains are derived by utilizing the center manifold theory and normal form reduction. Gain-amplitude curves for controlled systems are drawn and verified by numerical simulations. The formulae and expressions for the Langford system present a convenient approach to obtaining an effective analytical control in this system.