Abstract: The samples collected from a bituminous coal area formed by subvocanics in Yimin Brown Coal Field compose a series from brown coal to lean coal.Analysis of FTIR shows that oxygen-bearing functional group began to disapear in brown coal,alkyl and aromatic rings increase synchronously with increase of R°,reaching maxmium when R° is 1.10.Analysis of ESR and XRD shows that concentration of free radical and the ratio La/Lc of aromatic skeleton of the coal are between those of area-metamorphized coal and vocanics-contact metamorphized coal.Evolution of functional group is prior than that of aromatic skeleton and R°。