Devolatilization of the Refuse Derived Fuel(RDF) which is produced at WonJu in Korea was characterized in air atmosphere with variation of heating rate(10, 20 and 30 ℃/min) in TGA. The results of TG Analysis have shown that the pyrolysis and char combustion of the RDF occurred in the range of 350~700 ℃ depending on the heating rate. Activation energy of the RDF which was determined by using Friedman and Ozawa-Flynn-Wall method was in the range of 14.44~18.40 kcal/mol. Also, reaction order(n) and pre-exponential factors(A) were 1.219 and 3.02×10^(5) by using Friedman method, respectively. In order to find out the devolatilization mechanism of the RDF, twelve solid-state mechanisms defined by Coats Redfern Method were tested. The results of the Coats Redfern Method have shown that chemical reaction is the effective mechanism by comparison with the value of the activation energy which was derived from the Friedman and Flynn-Wall-Ozawa method and correlation coefficient from twelve solid-state mechanisms of Coats Redfern Method. The solid state decomposition mechanism of the RDF was found to be a decelerated F1 type, random nucleation with one nucleus on the individual particle.