For the purpose of opening up new application field of airborne electroma gnetic method, the Aerogeophysical Prospecting Section of IECG, based on sum ming up experience of previous workers, performed scientific trial flight of using airborne electromagnetic method to seek for fresh water in shallow fossil river bed in Nangong area, Hebei Province in November 1985. This paper re ports the tentative work of using regional characteristics of electromagnetic field and electromagnetic response to conduct "water quality mapping". It can be seen through the contrast between electrical distribution maps of different water qua lities in Nangong reservoir that this attempt reveals piactical prospects; for this method.