Whether tax shield (the debt tax shield and non-debt tax shield) can increase the value of a company has always been an important issue in corporate finance. This paper estimates the value of debt tax shield, clarifies the relation between tax shield and the value of the corporate operation, This paper applies reverse regression to estimate the values of debt tax shield in Taiwan listed cross section data. We find that debt and the value of the company are both positively related to size, the value that the net debt tax shield increases the value of the company. It is consistent with the result of Kemsley and Nissim (2002). The company can acquire an advantage on the corporate tax because of being in debt, consistent with the result of Green and Hollifield (2003).