Abstract: Coal preparation/mining can reduce the ineffective or harmful components of raw coal such as ash, sulfur and heavy metals. The resulting changes in mineral and organic components may affect the pyrolysis process and its kinetics, which is rarely reported in the literature. Raw coal from Shendong Coal-to-Liquid Coal Preparation R-YL and clean coal C-YL obtained from coal washing process were conducted pyrolysis experiments in TGA. The temperature was from room temperature to 1100°C, and the heating rate was 5, 10, and 20 K/min. The effects of coal preparation (coal washing) on the pyrolysis behavior of low-rank coal were studied. The results showed that the ash content of raw coal decreased from 9.12 to 4.69 wt.%, and the index of basicity changed from 1.92 (high alkalinity) to 0.68 (acidity). However, the organic components represented by functional groups were not changed a lot. In the primary pyrolysis stage (300～550℃), the maximum weight loss rates Dmax1 of clean coal pyrolysis at different heating rates were slightly lower because the washing reduced the catalytic performance of minerals. In the high-temperature pyrolysis stage (550～700℃), the maximum weight loss rates Dmax2 of raw coal were slightly higher at different heating rates, because most of the calcite removed from coal washing will be heated to decompose to CO2, which increased the weight loss rate.