Intracavity titling etalons were used to reduce the bandwidth of KrF laser output. The laser device used in our experimentS is a discharge pumped long pulse duration KrF excimer laser. its optical cavity consisted of a flat toeal reflector and a flat output coupler. Two apertures were placed inside the optical cavity to control the transverse modes, and three F-P etulons provided spectral dispersion. These etulons were 0.1 mm air-sacced, 0.5 mm solid, and 3 mm solid. In the experiments, the influence of the apertures and the reflectivity of output coupler were studied. By selecting suitable fparameters, output linewidth no more than 3 GHz can be obtained, this value is 1000 times smaller than the linewirth from free running.