In order to address how the newly-built hydrometry stations of small- and medium-sized rivers can be effectively used for flood warn -ing， this paper investigated the historical flood information of warning river reach， measured the elevation of riverside residences， and then estab-lished the relationship between the warning stations and socioeconomic factors of the river reach based on the technical strategy of investiga -tion and evaluation of flash floods. The technical system was then proposed to determine the specific water levels of hydrometry stations and warn -ing threshold values on the basis of current flood control capability.