Different population size is differentin consumption of water resources,different town scale have effect on water demand to a great extent.So studying on influence of population size on characteristic of water using is important to reveal characteristic of water consumption.This paper makes small town into three grades as large,medium,small-sized,according to township population of small town,chooses typical town to investigate,and receives water demand level of typical town through statisticcalculation.Also,to study the relationship between population size and the change of water consumption by analogism,and suggestthat coefficient of daily variation is from 1.75 to 1.95,while hourly variation is from 2.0 to 2.4,and higher as population size is smaller.