New approach to realizing high plasma parameters in electron cyclotron resonance discharge supported by microwave radiation in axisymmetric magnetic trap has been proposed. This approach is based on using the inverted radial distribution of plasma density (with minimum at the trap axis). Such plasma density distributions allow efficient cyclotron heating and sustaining the steady-state discharge with high plasma density including densities above the critical value (corresponding to the density for which plasma frequency equals to the frequency of heating radiation). Simulations of power deposition for EC heating of plasma with overcritical density in axisymmetric mirror magnetic trap are presented, in which the effect of increasing the heating efficiency for inverted radial plasma density profiles has been demonstrated.