Methods of sequential extraction are used to determine various chemical forms of metals in environmental samples. With the variety of different sequential extraction procedures used in environmental exploration studies, it is difficult to compare results between studies. The attempt of validation of methods of analysis of chemical fraction of Mn in ashes by FAAS method for two procedures of sequential extraction (BCR and Tessier et al.) was perfomed. It was found that both tested procedures give comparable and reproducible results. The optimal conditions of BCR methods were established, which are: parameters of ash sample (grain diameter – 0.06 mm, drying temperature – 110°C for 24 hrs, mass sample – 1.00 g) and parameters of sequential extraction process (time – 6 hrs, relation of mass of sample to the volume of extraction solution – 1:4). The optimum conditions of sequential extraction of Mn from coal fly ash can be applied in the study of chemical fraction of Mn in fly ash in different research laboratories.