Abstract: Developing microcomputer programs have been regarded as a effective way to expand the applications of numerical methods to rock engineering. This paper proposed a new core data-processing method on microcomputer programing of numerical methods so that core memory can be utilized as much as possible. Next, DYNPAK, a 2d FEM program on dynamic analysis, was improved according to the proposed method on a microcomputer. Finally, a case study was given as a application of the improved DYNPAK.