Abstract: We measured thermal conductivity of coal and rock samples with different porosity, moisture content, density and coal quality by the method of laser light scattering, and analyzed the influence of there factors on thermal conductivity of coal samples. We applied gray system theory to carry out grey relational analysis for thermal conductivity and influential factors. The results show that the coal thermal conductivity reduces totally with the increase of porosity, but does not monotonically; the thermal conductivity increases linearly with the increase of density; with the increase of moisture content of coal samples, thermal conductivity begins to rise rapidly and then leveled off; the primary influential factors of coal thermal conductivity were porosity, density and moisture.