MoS₂ was used as an efficient catalyst for hydropyrolysis (Hypy) of three samples of sedimentary organic matter with different maturities. Through comparison with Soxhlet extraction (SE),it was found that MoS₂ catalytic Hypy can remarkably promote the yields of total chloroform extracts,saturates, aromatics, hopanes and steranes. In addition, the difference of biomarker parameters indicated that isomerization of covalently-bound biomarkers is much more difficult than their free counterparts. Meanwhile, the high conversion of total organic carbon (TOC) in MoS₂ catalytic Hypy of organic matter proved that the presence of dispersed molybdenum sulfi de accelerated the breaking of C-C bonds and the release of hydrocarbons. To address the catalytic mechanism, a series of control experiments based on free Hypy and catalytic Hypy were conducted. The results showed that the calculated atomic ratio of carbon conversion/hydrogen conversion for catalytic Hypy was much larger than the presumed value of 1/2, indicating that intensive hydrogenation took place and significantly influenced the distribution of liquid products. Analysis of stable hydrogen isotope data, infrared spectra and m/z 83 ion chromatograph of the saturate fraction further confirmed this hypothesis. The difference of S content changing (ΔS) between catalyst-free Hypy and catalytic Hypy, and the thermal characteristics of the catalyst, indicated that active H₂S was defi nitely generated and it probably initiated free radical reactions in the early stage of hydropyrolysis of organic matter.