In the 21st century, one of the greatest challenges that the firms face is the rapidly changing environment. Under this circumstance, to continuously improve their performance to become more productive and competitive is very crucial for the firms to be sustainable. People is the key factor for success. How to select the right people by using a scientific and effective assessment tool becomes very important for a firm in its human resource management. This study is to understand and evaluate how the Assessment Centers are developed and used in the firms in Taiwan, how the Assessment Centers can further improve the effectiveness in the firms. This study aims to promote the use of Assessment Centers and to help the firms to increase their managerial capacity and competitiveness. This study used three studies of the firms who use Assessment Centers and explored various papers for references to get an integrated model of the Assessment Center. There are four major aspects for the firms to examine before they adopt the Assessment Centers approach: organization structures¡Bthe people¡Bthe flows and the resources in order to develop the most effective human resources management.