A tunable and wavelength stabilized KrF excimer laser has been developed. Two Fabry-Perot etalons of 2.4 THz and 170 GHz FSR are placed inside of the laser cavity to reduce the lasing bandwidth to 0.003 nm (3 pm). The wavelength was found to be tunable over a range from 248.1 nm to 248.6 nm. Within this tuning range, a stable wavelength setting to ±0.5 pm was achieved with a feedback system composed of a wavelength detector and a controlling mechanism. This wavelength-stabilized tunable KrF excimer laser will find its applications in optical microlithography, plasma diagnostics and photochemical reactions.