The thermal degradation of the homopolymer poly(methyl methacrylate) (PMMA) and flame-retardant tetrabromobisphenol-A (TBBA) as well as of their blends were carried out using the thermogravimetric method in the stream of nitrogen gas with 60㎖/min at various heating rate from 1 to 20℃/min. Friedman and Ozawa mathematical methods were used to obtain the value of activation energy.