A method of simultaneously quantitative measurement of the main elements (Si and Ba) in glass by using Laser-Induced Breakdown Spectroscopy(LIBS) was established. The LIBS system is composed of a Q pulse Nd: YAG laser, an echelle grating spectrometer and an ICCD detector. We collected the LIBS spectra of 4 glass samples. The Boltzmann curves of the main elements Si and Ba were established by using free calibration method. The contents of Si and Ba in glass samples were calculated with Boltzmann curves. The relative error of the contents of Si and Ba ranged from 4.96% to 10.12% and from 4.07% to 9.62%, respectively. The standard deviation of the contents of Si and Ba ranged from 0.38% to 1.29% and from 0.54% to 1.70%, respectively. T test results showed that there was no significant difference between the measured values and the actual values.