In the article, with the help of IR-spectroscopy, DTA-analysis and diffractometric X-ray luminescence analysis, our studies of the composition and flame-retardant properties of industrial complex flame retardants of unknown composition based on antimony oxides were carried out, and a new mechanism of their flame-retardant and stabilizing action was proposed based on the determined composition of industrial flame retardants , which include antimony oxides and calcium carbonate identified by us.. In the work, experimental studies were carried out and qualitative IR spectral analysis and quantitative calculation of IR curves based on the results of the study of industrial samples of flame retardants based on Sb2O3 were performed. Based on the analysis of the IR spectrum, new organic substances were identified in the Sb2O3 samples. Additional thermal decomposition of all samples by DTA analysis for all samples of Sb2O3 flame retardants begins to lose volatile substances and moisture at 50–80°C, while losses at 500–530°C can reach from 1.97% to 3.7% for 4 samples. Your flame retardant samples, based on X-ray fluorescence spectroscopy, on a diffractometer, as it was determined, consist of two phases, two inorganic components, namely antimony trioxide – Sb2O3 and an additional component of microcrystalline calcium carbonate – CaCO3 with impurities of organic substances, in appropriate quantities . The work proposed an improved chemistry and reaction mechanism of stabilization and flame retardant action of complex flame retardant for PVC-linoleum compositions, in a large temperature range from 80°C to 1000°C