Abstract: Different working face advancing speeds cause different loading rates on overlying strata, which makes the roofs showing different tensile strengths, so it's very important for investigating the strata-pressure behavior how loading rate impacts on the tensile strength of rock.In this paper, two kinds of loading rates were defined after analyzing overburden migration laws, including external force loading rate and displacement loading rate.Then the law that tensile strength is bigger under the higher loading rate was obtained in Brazilian split test.And then the mechanism of external force loading rate and displacement loading rate impact on tensile strength was analyzed by using the elastic dynamics method and the principle of work-power in molecular scale.At last, the impact on the tensile strength of loading rate was verified after the transient dynamic analysis on Brazilian split test by using ANSYS/LS-DYNA.It was found that inertia force varies with external force loading rate and the kinetic energy of rock while breaking varies with displacement loading rate, so there will be different tensile strengths under different loading rates.