本文立基於Merton(1974)或有求償權評價法及Leland(1994)內生破產資本結構模型上，加入次順位債券的考量，建立一個連續時間資本結構分析模型，量化的資本結構可作為企業融資之決策依據。內生破產行為與風險移轉行為都是股東與債權人之間可能產生的代理問題，本文的模型不但分析這兩種代理問題，更計算其所產生的代理成本。由模擬的結果發現內生破產成本雖然不大，但是其對無風險利率及公司非槓桿價值的波動度卻是非常的敏感。在本文的模型下，只要債務契約不能重新訂立，次順位債券的發行永遠都會降低優先債務的價值。在本模型中次順位債券的風險貼水比優先債券的風險貼水高；但是本文發現不管是優先債券或是次順位債券的風險貼水，當公司接近宣告破產時，公司非槓桿價值的波動度對兩種債券風險貼水的影響出現高風險低報酬的現象，可能的解釋理由如下：當公司接近宣告破產時，公司非槓桿價值波動度的增加使破產可能性提高，進而使風險貼水減少的間接力量大於波動度增加直接使風險貼水上升的力量。 / Based on Merton(1974) and Leland(1994), we construct a continuous-time capital structure model with subordinated debt. Quantitative results may serve the guidance of financial policy of the firm. Both endogenous bankruptcy and risk shifting behaviors are the agency problems between the equityholders and debtholders. Based on our model, the agency problems is considered and the agency costs are calculated. From the result of simulation, endogenous bankruptcy agency cost is small but sensitive to the volatility of unlevered asset value of the firm. Under renegotiation-proof, the senior debt is harmed by the issuance of the subordinated debt in our model. The risk premium of the subordinate debt is higher than that of the senior debt is confirmed by the model, however, when the firm is near bankruptcy, the behavior of "high risk high return" of both debts is reversed. The reason for the junk bond behavior may be explained as the negative effect of risk premiums due to the increase of the probability of bankruptcy is higher than the positive effect of the greater risk caused by higher volatility.