本文主要研究內外部公司治理機制對獨特性風險之影響，探究降低特性風險的治理機制。本研究利用所有權結構、董事會組成、經理人激動機制、資訊透明度、法律制度規範與産品市場競爭等六稱公司治理機制並考慮GARCH效果修正Xu and Malkiel (2003)的獨特性風險衡量方法，探詩2002年至2007年台灣上市公司之公司治理機制獨特性風險之影響。實證結果發現外部主要股東持股比例愈高、獨立董監事佔監事席次愈多、經理人持股比例愈高以及資訊愈及時，公司獨特性風險愈低，顯示較佳的內部公司治理機制，可以降低公司獨特性風險。然而，法律制度規範與産品市場競爭等外部治理機制並無法降低獨特性風險。

This paper tries to discover the key corporate governance mechanisms that can reduce idiosyncratic risk/unsystematic risk which is the specific risk that associated with firms' operating. Take the GARCH effects info consideration and further modify the measurement of idiosyncratic risk proposed by Xu and Malkiel (2003), we employ ownership structure, board composition, managerial incentive, information transparency, legal infrastructure, and product market competition to investigate how the internal and external corporate governance mechanisms impact on Taiwanese firms' idiosyncratic risk from 2002 to 2007. Empirical results indicate that firm with better internal corporate governance mechanisms such as higher outside block-holder ownership, more independent directors and supervisors in the board, higher managerial ownership and more information timeliness, associates with lower idiosyncratic risk. However, the external corporate governance mechanisms are not helpful for reducing idiosyncratic risk.