Inductively coupled plasma atomic emission spectrometry (ICP-AES) and flame spectrometry are used to establish the stoichiometric composition of Li6Gd(BO3)3, Li5.4Na0.6Gd(BO3)3, LaB3O6, and SrB4O7 single crystals, including cerium-doped crystals. It is shown that flame spectrometry is more advantageous for analysis of pure borate crystals. ICP-AES is more universal and allows determining basic elements and admixtures independently of solvents used for decomposition of borate samples. Both methods provide sufficient accuracy of the analysis.