Abstract: In order to study the effect of rock-coal strength ratio and coal-rock height ratio on mechanical properties of coal-rock combination, the particle flow software PFC^2D was used to carry out simulation study for coal rock with different rock-coal strength ratio and coal-rock height ratio. The results showed that combination models of fracture pattern could be divided into four types, such as the V-shaped shear fracture of coal, the single shear fracture of coal, the X-shaped shear fracture of coal and the shear failure of coal and rock. With the decrease of height ratio of coal and rock, the impact energy index firstly increased, and then decreased. However, with the increase of rock-coal strength ratio, the impact energy index decreased gradually; the ultimate compressive strength and elastic modulus increased with the decrease of coal-rock height ratio, while the elastic modulus also increased with the increase of rock-coal strength ratio, and the ultimate compressive strength tended to be a steady value.