A parametric study on the material properties of the brain tissues was conducted using the 2-D porcine brain model developed by Zhou et al (1994). The animal test condition by Meaney et al (1993) was simulated. Four points in the DAI regions were chosen for evaluation. Changes due to variation of material properties were investigated in terms of shear stress distribution, shear stress magnitude, shear strain magnitude, shear stress time history, shear strain time history, and strain rate. Base on the simulation results, a stress criterion of 20 kPa and a strain criterion of 0.20 were proposed for DAI to occur in the mini pigs. Shear stress/strain contours can be used for DAI predictions. Diffuse axonal injury was found to occur in areas where higher shear stresses or strains persisted for relatively longer periods during impact. It was estimated that the instantaneous shear modulus is in the range of 40 kPa to 120 kPa and the long term shear modulus is in the range of 5 kPa to 8 kPa. The decay factor should be within the range of 350 s−1 and 700 s−1.