A modified Split Hopkinson Pressure Bar (SHPB) system is used to determine the mechanical properties of soft and ultra-soft materials. An aluminum bar is introduced to reduce the impedance mismatch between the test system and sample. The small signal of the forces was measured by a quartz crystal gauge system. The high precision Laser gap gauge (LGG) system was used to measure the deformation of samples. The compressive tests of Cemented Paste Backfill (CPB), fresh CPB and Polymethylmethacrylate (PMMA) and the fracture toughness tests of PMMA were conducted to approve the legitimacy of our modified SHPB system. From these experiments, the efficiency and economy of the modified SHPB system were attested.