This paper proposes three theoretical hypothesizes about credit policy, enterprise-bank relation and capital structure through detailed theoretical derivation. Next, all hypothesizes are tested used 765 listing companies between 2003 and 2012 as sample. The result show credit policy and enterprise-bank relation has significant positive effect on capital structure and there is a substitution relationship between them．Therefore, In order to broaden the financing channels of the enterprise and reduce the enterprise’s financing cost, multi-capital market should be speed up. Government should pay attention to the informal institutional arrangement (enterprise-bank relation) for the role of corporate capital structure, prevent or reduce the occurrence of irregularities.