Abstract: In this paper a cesium beam maser is proposed in which the optically pumping state selection technique by two laser beams is used together with the atom storage bulb technique.The density matrix theory is used to analyse the maser oscillation conditions.The relation between the maser oscillation power and the flux of the atoms entering the bulb is derived.Assuming the use of a TE₀₂₁ mode cavity and a annular quartz bulb coated with Paraffin, the maser oscillation power and its linewidth as well as the filling factor of the cavity are evaluated.The expected short term stability of the maser is also given.A similar maser scheme with two atom beams and two separated blubs is presented too.