Abstract:The hole depth (charge length) is one of the factors to influence the character of blast wave in rock. Using the difference code SMMIC developed by the authors,the spread process of the blast wave in the vertical hole with single free surface is analysed. The results indicate that the decay coefficient of the peak value of blast wave with the distance will be reduced as the hole depth (charge length) is increased. The decay coefficients of the peak value of blast wave with the distance are 1.35 and 1.56 corresponding to 4 m and 2 m deep holes respectively.