The reactivity of O-methylated and reductively methylated coals were tested for noncatalytic liquefaction reactions in tetralin solvent at 693 and 723 K to evaluate the effect of methylation on the conversion of Illinois No. 6 coal. For the liquefaction test at 693 K, the oil yield from reductively methylated coal drastically increased from 37 to 60 wt % compared with the raw coal. On the other hand, the oil yield of O-methylated coal was approximately 50 wt %. The improvement of oil yield for methylated coals was related to the number of methyl groups introduced by methylation. The increased oil yield for methylated coals was due to the acceleration of the decomposition reaction for preasphaltene. The difference in oil yield between raw and methylated coals decreased with increasing reaction temperature to 723 K, but an improvement of oil yield was observed. These results indicated that the methylation of coal molecules was effective for the production of the oil fraction, especially under lower severity conditions.