Airborne electromagnetic (AEM) systems were first developed in the early 1950's in Canada and Scandinavia. AEM systems have been applied in mineral exploration, geological mapping, geohydrological investigation and environmental monitoring in China since the 1980's. A dual-frequency AEM system (463 Hz, 1,563 Hz) which was developed by IGGE in the early 1980's has surveyed more than 160,000 line-km. A new three-frequency AEM system was also developed by IGGE in 1999. In 2001, a survey was conducted in Qian'an, Jilin Province, using the new AEM system. The purpose of this survey was to delineate salinization, to determine the freshwater/saltwater interface and to explore the freshwater resource for catchment management such as drinking, agriculture, stock raising and wetland protection. The main purpose was achieved by this survey. For the salinization study, the upper frequency AEM data were used. By comparing the apparent resistivities calculated from the AEM data with the geohydrological data, the areas and intensity of salinization were identified. For the freshwater resource study, lower and middle frequency AEM data were applied. Two zones of fresh ground-water were determined within the achievable exploration depth (about 100 m) of the AEM system.