A possible maximum amplitude of the streamers is addressed. A model equation of the coupled system of drift waves and streamers is described from wave-kinetic equations, assuming that zonal flows are absent. Steady state solutions are obtained and the dynamical behaviors are examined. The influence of the nonlinear self-stabilizing effect is investigated. An upper bound of the amplitude of the streamers is given, in the limit of the vanishing damping rate of streamers, which corresponds to the equi-partition between streamers and drift waves.