本文以審計人員市場佔有率與客戶集中度之綜合衡量補捉審計品質，並以Jones模式衡量裁量性應計數，利用自願性預測情境凸顯不同的裁量性應計數特性，藉此探討審計品質與不同特性的裁量性應計數之關聯性。為避免實證代理變數之衡量誤差影響結果，研究設計乃採用實驗組預測公司與對照組未預測公司相比較，以凸顯出前者之裁量性應計數特性。實證結果顯示：預測盈餘增加公司之裁量性應計數，於預測前一年具有透露和有資訊之特性，而於預測當年卻具有投機特性，其中高審計品質群組不僅顯著具有發放和有訊息之特性，投機特性亦顯著；預測盈餘減少公司於預測當年，會利用裁量性應計項目使會計盈餘更佳反映公司績效，且高低審計品質組問差異顯著。此顯示，當管理者預測盈餘增加，財務報表使用者需注意公司是否利用應計裁量權操弄盈餘。就審計此一提昇資訊品質之機制而官，經高品質審計之裁量性應計數可提升會計盈餘之價值攸關性。但在消極面減少財務報告雜訊上，本研究結果卻發現高品質審計人員並未有效遏阻具投機性質的裁量性應計項目。 This research examined the effects of audit quality on the characteristics of discretionary accruals based on firms voluntarily forecasted their earnings (hereafter the forecast firms). Discretionary accruals were estimated using a cross-sectional version of the Jones model. In contrast of prior research, the audit quality was captured by a combined measure of the auditor's market share and client concentration. The market share measured the auditor's competence (industry specialty) and the client concentration measured the auditor's independence. To reduce the impact of measurement errors of proxy variables, a design of group comparisons was employed to make the pattern of discretionary accruals of the forecast firms more evident. The results showed that firms with optimistic forecasts used discretionary accruals, in the year before earning forecasts were announced, to signal future cash flows. However, it later managed earnings opportunistically in the forecast year. Stronger associations between discretionary accruals and future cash flows were documented for optimistic forecast firms audited by higher quality auditors. Firms with pessimistic forecasts used discretionary accruals to make earnings better reflect firms' performance and hence, decreased the serial correlation of changes in earnings. Significant difference in the pattern of changes in earnings was observed between pessimistic forecast firms audited by lower quality auditors and those audited by higher quality auditors. As a means of information disclosure, voluntary forecasts that exceeded the previous realized pretax earnings were not necessarily credible. In respect of the impact of auditing function on management forecast, audit quality was strongly associated with signaling discretionary accruals, but could not deter opportunistic discretionary accruals effectively.