In this study, a computer program to design a tunnel - blasting pattern was developed. The program consists of two parts ; one is for the tunnel blasting design and the other is for the blasting modeling to estimate the peak particle velocity, the excavation damage zone and the fragmentation distribution. The design method of tunnel blasting pattern suggested by Langefors1) was modified to produce the model. In addition the correlation between the rock mass rating, i.e., the RMR, and the rock constant in blasting, c, was analyzed based on the data collected from 23 tunnel blasting tests. The correlation between them was good enough to be applied in cut design. Furthermore, the developed program is capable of estimating the particle velocity by using (1) the existing vibration equations and (2) the vibration equation obtained by test blasting to examine the practical applicability of the designed blasting pattern.