The research in the field of strategic human resource management argues that one of the sources for competitive advantages of a firm is the human capital in the firm and attempts to find out ways to attain the organizational goals; to increase motivation and job skills of employees and to improve the firm performance. Recently, many studies show the effectiveness of the high performance work systems to increase the performance of firms. By introducing a series of human resource management practices which are complementary to each other, high performance work systems can increase the financial performance such as sales level, net profit,or return on assets as well as non-financial performance such as commitment, satisfaction,or discretionary behaviors of employees. Previous studies on the high performance work systems explain the positive effect of the internal fit between HR practices and the positive effect of the fit between HR practices and organizational situation. However, there are only a handful of studies which investigate these fits empirically in Korea. Based on the categorization of the high performance work systems into three different types of HR practices, such as ability-enhancing HR practices, motivation-enhancing HR practices,and opportunity-enhancing HR practices, this study attempts to show the positive interaction effects between these three types of HR practices on the performance of firms and also show the positive moderating effect of employees’ positive perception toward their managers in the relationship between high performance work systems and firm performance. This study uses the data which were collected in the first wave of the ‘Human Capital Corporate Panel Survey’ conducted by Korea Research Institute of Vocational Education & Training. The ‘Human Capital Corporate Panel Survey’ is a long term study of HR practices of firms, their employees’ attitudes, and financial performance. Sampling is consisted of ‘corporate sampling’ and ‘employee sampling’. Corporate survey samples are 441 firms including manufacturing,non-financial service, and financial service corporations and the target of the survey is HR managers in each firm. The results show that financial performance can be increased more when firms introduce different but complementary HR practices at the same time and that the positive perception of employees toward managers strengthen the association level between high performance work systems and firm performance measured by sales level of a firm. Even if there are some limitations, such as the causality issue and the measurement issue,this study has several implications. First, in terms of introducing HR practices, it would be better to choose a series of HR practices which are complementary to each other. The effectiveness of introducing new HR practices can be maximized when organizations attempt to implement HR practices which have similar effects on the behaviors or attitudes of employees. Second,communication with employees and making trust between management and employees are important for the successful implementation of new HR practices.