Time of Flight (TOF) mass spectrometry is one of the most important methods for analysis of materials. In this method, the ions, produced by an ionization source, are accelerated in a uniform electric field and then separated in a field free region based on their mass to charge ratio and thus will arrive to detector at different times. Any mass spectrometer requires mass calibration to determine accurate mass of unknown species. Usually standard masses are used for accurate calibration. In this thesis, the TOF mass spectrometer design and constructed in the department of chemistry was calibrated using alkali salts as standard substances. In this work, an Nd:YAG laser at third harmonic (355 nm) with 10 ns pulses was used as a desorption/ionization source. Irradiation of high-power laser on a solid surface caused rapid melting and vaporization of the materials followed by atomization, excitation and ionization. Thin aluminum foil was used as a support to hold the sample in the ionization region. The support was mounted as a repeller in the accelerator. The support was made in contact with aqueous solutions of alkali halides (0.1M). After drying the sample and closing the vacuum chamber, vacuum was established using two rotary and two turbo molecular pumps. Ultimate vacuum of 10 -7 mbar was achieved. Laser was then aligned to irradiate the sample through a quartz window. The laser beam was focused to enhance evaporation and ionization of the sample. Time of flight spectra of individual alkali halides including LiCl, NaCl, KCl, RbCl, CsCl were recorded. Approximate masses were calculated from the m/z = 2eUT 2 /D 2 , where U is the applied voltage to the accelerator and T and D are the flight time and length, respectively. It was found that all alkali halides produce ions of M + , and M + .(MX) n type, where n=1,2,3, M = the alkali atom in the salt and X is its counter halide ion. Taking accurate masses of the known ions, a calibration curve was obtained by plotting m 1/2 versus flight time, using m 1/2 = aT+b . Using this calibration curve, Al + ion is also identified. Binary and ternary mixtures of alkali salts were also used to obtain more accurate mass calibration. For more accurate calibration a mixture of all alkali chlorides were used. By this a broad range of flight times were covered by different ions. An average mass accuracy of 0.04 % was obtained.