In the process of credit investigation and review，some indicators or singals are found in the regulations of state-owned banks，which are designed to screen and reduce the loan risks，to determine whether to lend the enterprises and manage the lending activities after loan. However，the operations of loan are impacted by various social norms inevitablely.

The author details one case HY branch of bank that is very special for its “dual” loan structure. The phenomenon of its formation is mainly due to the transferring of “industry indicator” to the “ownership indicator”，which mainly affected by the mechanism of “shirking responsibily”. In an ideal type of credit investigation and review，the financial statements as the core of the indicator are widely questioned，but it does not shape a similar “lemon market” for adverse selection，because each bank has the different ability of analyzing financial statements，the impact of various social norms，the weaker banks will find alternative “character indicator” and other informal indicators to prevent loan risks，those honest borrowers will not be completely expelled from the credit market.

In this paper，the author describes the process of state-owned bank credit investigation and loan review process，describes the transformation of formal indicators，analyzed the emerge of alternative informal Indicator in the various social norms，and discusses the mechanism of shirking responsibility and the stability of micro-instituions simply.