The limit cycle oscillation for a cantilever plate in a uniform flow stream is investigated in this paper. von&;#183;Karman's theory for a large deflection plate and quasi-steady aerodynamic theory are assumed. The equations for computing the nonlinear oscillation of a fluttering cantilever plate are derived by means of Rayleigh-Ritz approach. Lagra-nge' s equations and a set of mode function expansions are empoloyed. Time marching simulation is used to determine the limit cycle oscillation and fluttering boundary. The results indicate that the modal expansion is of convergence. The length-to-width ratio of a plate has a great effect on flutter amplitude of limit cycle.