Asymmetric information,which is defined that there are differences in knowledge of information for each parties of contract,exists in economic activities extensively.Furthermore,moral hazard and adverse selection are a pair of inevitable outcomes of asymmetric information.Since the deposit insurance system was established in westem courtries,it had always been disturbed by asymmetric-irformation.And the deposit insurance system is doubted by the authorities in many countries because of moral hazard and adverse selection.