中文摘要：

国有银行的信贷支持不足是造成中小企业融资困境的主因。从国有银行的经营目标及其约束条件出发，运用委托-代理理论，对国有银行的信贷行为选择机理进行分析，不难发现，其对中小企业信贷支持不足的根源主要在于相关政策和环境不能满足其目标约束、参与约束和激励相容约束条件。为此，政策设计既要考虑宏观整体目标，更要考虑微观个体的行为选择，以增强政策的实施效果。

英文摘要：

Insufficient credit loan support from the state - owned bank is a main cause for financing predicament in small - and medium - sized firms. Starting from the operation target of the state - owned banks and their binding terms, by using entrust - deputizing theories, through an analysis on credit loan behavior choosing mechanism of the state - owned bank. It＇s easily seen that their insufficient support for small and medium - sized firms resulted mainly from the related policy and environment＇s incapability to satisfy their target control, participation binding and incentive compatible binding terms. For this, it＇s necessary for policy design to consider the macroscopic target as a whole, and above all, the individual behavior in a tiny view to enhance the execution result of policy.