In order to retain customers and rise organization's benefits, many industries invest in customer relationship management (CRM) system; Therefore, there are many researches focus on discussing key success factors of implementing CRM, but they neglected the importance of performance after implementation. In order to understand the effectiveness of implementing CRM and how to increase performance, this study uses 16 banks which have already applied CRM in Taiwan, to apply data envelopment analysis (DEA) to measure their CRM performances. Evaluating performance is based on financial and non-financial to find the efficient banks. Besides, it also gives some suggestions for non-efficient banks to improve their performances.