This research investigated and built up a knowledge base which was used primarily in the nuclear core loading pattern design and safety analyses for the Maanshan Nuclear Power Plant in Taiwan. In this study, a rule-base knowledge representation method was employed to provide appraoches for dealing with various situations in the core loading pattern design and a practical example of a condition that the design criteria were violated was simulated. In the simulation, the core loading pattern was adjusted according to the suggestions based upon the knowledge base, in order to verify the accuracy of the knowledge base. In the practical simulation, a graphical user-interface program, XIMAGE-PWR/SIMAN, imported from USA, was used to display the core loading pattern in graphics. The program, used together with a core steady-state simulation code, SIMULATE-3, and also imported from USA, provided the results of calculation of core parameters related to the core loading pattern design and therefore, facilitated the core loading pattern design efficiently.