Abstract: This paper presents The investigation of laser resonance ionization mass spectroscopy of lutetium with our laser ionization mass spectrometry system manufactured by our own. The optimum radius of laser focal spot overlapped with atomic beam is calculated theoretical.Lutetium ionic signal at The rate of 1.8 ×10~5 s- ~(1)is detected The Sample she of 1 μg lutetium.. With laser resonance ionization and The of atomizer,it is possible that The detection ho reaches 10~6 atoms. The effect of laser-induce isotopic discrimination on The measurement of isotope ratio is discussed. It is proposed that laser bandwidth and wavelength tuning effects are The main factors of deviation of lutetium isotopic ratios with this broad bandwidth laser.