Abstract: The coal facies association, peat swamp types and its formation conditions of coal seam B₁ in Pingdingshan mining area are studied by way of the coal petrology and coal chemistry. Two coal facies are distinguished:reduction facies and oxydation facies. Both have qualitative and quantitative index. Coal B₁ is composed of three or four succession from reduction facies to oxydation facies, showing the development from forest swamp to marsh upwards. This succession probably represents the seam formed in flat coastal plain environment. It was autochthonouslly partly hypautochthonousely deposited in raised swamp under ombrogenous, oligotrophic conditions B₁ was formated in freshwater peat swamp, but the top of the seam show brackish influences.