Abstract: A experiment system was built based on laser resonance ionization and time of flight mass spectrometer, which was used for measuring the parameters of the atomic energy level structure. The design principle, overall structure, properties characterization and application of the mass spectrometer system were described in detail. The system was consist of atomization furnace which used to heat up the metal sample to form atomic vapor, laser resonance ionization system based on pulsed dye laser pumped by Nd:YAG solid-state laser, time of fight mass analyzer which adopted double-field acceleration and double-field reflection technology. Experimental result showed that the mass resolution under the laser resonance ionization source was better than 1 300 FWHM and the dynamic range was better than three orders of magnitude. Based on the mass spectrometer, the atomic energy level experiments of metal neodymium were conducted and the isotope shift was obtained. This system had great value in the aspect of atomic energy level structure research of the lanthanides and actinides to solve the problem of the lack of key spectroscopy parameters like isotope shift and autoionization states.