Abstract: An optical emission spectroscopy method had been applied to diagnose titanium hydride vacuum arc discharge plasmas. Based on the emission spectra theory of the local thermodynamic equilibrium plasma, a plasma emission spectral fitting model was developed to analyse the emission spectra of the vacuum arc discharge plasmas. Comparing the fitting spectral and the observed spectral in the region of 330-340 nm and 498-503 nm respectively, good agreement was found between the predicted and observed spectra. Since this model calculated the summation of Voigt profiles of all spectral lines in the concerned range, it overcame the extraction of intensity and broadening from the overlapped lines by conventional Boltzmann plot method. Furthermore, the emission spectra, density, and temperature of the vacuum arc discharge plasmas under different discharge conditions were studied. The results indicated that the temperature of the TiH vacuum arc discharge plasmas were about 1 eV, and the generated hydrogen atoms were more than the titanium atoms. At the same time, with the increasing feed-in power to vacuum arc ion source discharge, more hydrogen atoms were desorbed from the electrode than the electrode metal atoms erupted, which was benefit for the application of neutron generator.