Isothermal subcritical water extraction technique was used to extract organic matters from Huadian oil shale under different extraction conditions. The effects of particle size, extraction temperature, extraction time, and water oil shale mass ratio were investigated on the extracts yield. A series of extraction experiments were carried out with three particle size samples and the water oil shale mass ratio in the range 1.5-3.5 at five levels of temperature for 5-70 h. As a result, extraction temperature and extraction time were found to have large effect on the extracts yield, and the particle size had large effect on the extracts yield at 335 degrees C. The maximum extracts yield could be obtained at 365 degrees C for 30 h with the water oil shale mass ratio of 3 using middle particle size oil shale samples. Gas chromatography mass spectrometry (GC-MS) analysis of the n-hexane-soluble maltene in bitumen 1 and the organic matters in the spent aqueous solution demonstrated that large molecular hydrocarbons could be cracked into smaller hydrocarbon compounds with the extending of extraction time. The elemental analysis of the bitumen 1 showed that the atomic H/C reached the maximum value of 1.82 wt % when the extraction time was 15 h. The analysis results of the pyrolysate indicated that subcritical water played the roles of catalytic pyrolysis and extraction solvent during extraction process.