In this paper, we propose a new technique of case-base maintenance. The weighted association-based case reduction technique (WACRT) can reduce the size of the case-base in order to enhance the efficiency while maintaining or even improving the accuracy of the CBR. The weighted association rules do not use the property “all subsets of a frequent item set are frequent”. It is pruned by the “k-support bound”. The experiments on the engine design system have shown superior generalization accuracy for CBR with WACRT as well as a greater solving efficiency.