Abstract: An electrolytic solution for Karl Fischer's coulometric titration comprising a iodide ion, sulfur dioxide, a basic compound and a solvent, and a method for measuring a water content using the same are disclosed. In the electrolytic solution, the basic compound is a mixture comprising an amino alcohol and a compound represented by formula (I): ##STR1## wherein n represents an integer of from 1 to 3, the amino alcohol is present at a molar ratio of not more than 1 to sulfur dioxide, and the amino alcohol and compound represented by formula (I) is present at a total molar ratio of from 1 to 5 to sulfur dioxide. The electrolytic solution is free from a pyridine odor, applicable either as an anolyte or as a catholyte, and capable of considerably reducing time required for water content measurement.