Abstract:Splitting Hopkinson pressure bar which diameter is 74mm was used to investigate the tensile mechanical properties of cement mortar flattened Brazilian disc under high strain rate. Dynamic mechanical behavior of cement mortar under the strain rate from 50/s to 342/s was obtained by controlling different air pressure. Comparison was made with traditional Brazilian disc to verify the rationality of the experiment. The result shows that the splitting strength, the critical strain and the Young’s modulus increase with the increase of the strain rate, DIF obtained by experiment is in agreement with the model provided by CEB. And the pattern of fracture is related to the strain rate, the shear fracture area increase with the increase of the strain rate. Flattened Brazilian disc is better than Brazilian disc as a way of measuring tensile mechanical behavior of brittle materials indirectly.