本文旨在檢視審計品質與資訊不對稱之直接關聯。過去文獻多以審計品質作為資訊不對稱風險的代理變數，探討審計品質對資金成本的經濟影響，間接推論高審計品質隱含低資訊不對稱程度，能使企業資金成本下降。不同於過去文獻，本文採用優勢資訊交易機率（probability of information-based trading，簡稱PIN）擷取企業私有資訊交易的頻率，據此直接衡量企業資訊不對稱的程度；另以會計師事務所規模、會計師查核任期、裁決性應計數與審計市場產業專家作為審計品質的代理變數，實證結果證實審計品質確實能降低企業的資訊不對稱。本文填補了過去文獻尚未連結的部分，並且提出臺灣大型會計師事務所能降低企業資訊不對稱，具有較高的審計品質之實證證據。

The purpose of this study is to examine the relationship between audit quality and information asymmetry. Audit quality, the proxy variable representing information asymmetry widely in most studies, can affect firms' cost of capital. To differentiate from prior studies relating audit quality as the proxy variable, our study adopts probability of information-base trading (also named as PIN). PIN utilizes the possibility of informed traders trading stocks in capital market, as direct variable to evaluate the level of firm's information asymmetry. In addition, the size of audit firms, audit tenure, the discretionary accruals and the experts in audit market are also designed as proxy variables of audit quality. Based on empirical results, we prove that audit quality can significantly reduce information asymmetry. This study not only complements the linkages between audit quality and information asymmetry that prior studies didn't provide, but it also proves this with large audit firms in Taiwan, implying capability of higher audit quality, can effectively reduce information asymmetry.