The shareholder’s value plays an important role in corporate default decisions. However, in traditional structural model, the shareholder’s value is unreasonablly measured by the part of corporate asset value to shareholders. Based on asset value decomposition, this paper measures the shareholder’s value by the combination of the part of corporate assets to shareholders and the so called liquidity option. Technically, we describe the liquidity option as a permanent American put option and introduce it into the traditional structural model. We prove that traditional structural models are special cases of the new model only under unrealistic conditions. But under normal conditions, the traditional structural models will be unreasonable and tend to underestimate the corrporate debt yield. We also prove that our new model can correct this mistake and adapt the more volatile stock data well and thus give much more stable pricing results．