Abstract: The mineral composition and the microstructure of mudstone play a decisive role in its mechanical properties. The mudstone in Jurassic coal measures was studied using XRD, SEM and rock mechanics test system, and simultaneously acoustic velocity of the mudstone was tested. The correlations between mechanical properties and mineral composition as well as microstructure of mudstones have been established. The results show that the mudstone of Jurassic coal measures in Shendong Mining Area is mainly composed of quartz and clay minerals with mean contents of 55.22% and 26.67% respectively. Whereas, mean contents of quartz and clay minerals of mudstones in Carboniferous Permian coal-bearing strata are 31.90% and 63.24% with difference of 23.32% and 36.57% respectively, which resulted in lower mechanical properties than that of Jurassic mudstones. With the increase of quartz content, the uniaxial compressive strength and elastic modulus show an increasing trend, while, with the increase of clay minerals content, the trend is opposite. Meanwhile, the acoustic velocity, uniaxial compressive strength and elastic modulus increase with the increase of mudstone density.