Time of flight (TOF) mass spectrometry (MS) is one of the most sensitive and widely used methods for material analysis. In TOF-MS molecules are ionized, accelerated and separated in a field free region. In fact, ions of different m/z are dispersed in time during their flight along a field free drift path of known length. The lighter ones will arrive earlier at the detector than the heavier ones. Compared to other mass analyzers, including magnetic sectors, quadrupole and ion traps, TOF can readily reach mass resolving power of 10000 or more with very high efficiency. Since in TOF mass spectrometry, a complete mass spectrum is generated in only microseconds, the “instantaneous” data acquisition allows signal-averaging to increase the signal-to-noise ratio in short analysis times. In this work mass spectra of earth alkaline halides have been studied using laser ionization technique and a homemade time of flight mass spectrometer constructed in Isfahan University of Technology. The spectrometer is a linear TOF and was operated in positive-ion detection mode. Solid samples were coated on a plate acted as the repeller in the accelerator. The plate was then irradiate with an Nd:YAG laser light at third harmonic (355nm). The vacuum of the TOF mass spectrometer was kept at 10 -7 mbar during the experiments. Background mass spectrum of stainless steel plate and aluminum foil as supporting plate were recorded. Aluminum foil was better since a fresh one can be used for each substance and its background mass spectrum was more privacy than that of stainless steel. Time of flight spectra of MgCl 2 , CaCl 2 , SrCl 2 and BaCl 2 were recorded and assigned. To assign the peaks, approximate masses were first calculated using the calibration curve was then obtained by plotting the square root of standard masses versus flight times. In mass spectra of CaCl 2 , SrCl 2 and BaCl 2 , ions of M + , MCl + and MCl + (MCl 2 ) with different isotopes were identified where M is alkali earth atom. To support the assignments, the isotope patterns of the M + and MCl + peaks were simulated. A Gaussian shape function was considered for each peak. The intensity for each peak was taken as the product of natural abundances of atoms present in the ion and reported in the literature. All peaks were generated with same width while the most intense peak in isotope pattern was considered as the base peak. Very good agreement was observed between simulation and experimental spectra.