中文摘要：

以中国1999-2008年能源行业上市公司的平衡面板数据为样本,运用非线性计量方法—面板门限模型,实证分析资本结构与经营绩效的关系。以Tobinq值作为经营绩效衡量指标进行负债（资产负债率）门限测试,实证结果发现：存在单一门限效果,其门限值为26.4%,其区间上下影响系数分别为正相关、负相关,并且都很显著,即存在一正一负的非线性关系。对我国能源行业上市公司来说,适度的利用财务杠杆、提高资产负债率,可以提高经营绩效;但是过度使用财务杠杆会增大企业财务风险并无法有效提高经营绩效。因此,企业经营管理者应在适度的范围内,合理运用财务杠杆,实现股东财富最大化的目标。

英文摘要：

With a sample of 68 listed companies in energy industry from 1999 to 2008,the paper studies the relationship between the company performances and the capital structure.We use nonlinear panel threshold regression model to observe balance panel data to test if there exists an optimal debt（total asset ratio）which may result in threshold effect and asymmetrical responses of the company performances to the debt total asset ratio.Tobin q is selected as the proxy variables to represent the company performances.The empirical results shows there is only one single threshold effect,while all of the observations can be divided into two ＂regimes＂ depending on whether the debt ratio is smaller or larger than the specific threshold value（26.4%）.It shows nonlinear relationship exists.Two coefficients are both positive and negative.The appropriate use of financial leverage and improving asset-liability ratio can improve the performances of the company;but excessive use of financial leverage will increase the enterprise＇s financial risk and can not effectively improve the performance of the company.It suggests that financial managers should use financial leverage wisely in order to maximize the company performances and stockholders＇ welfare.