This article described systematically the principle and key instruments for measuring and assessing the coastal land groundwater salinity, which was based on ElectroMagnetic(EM) inducing theory. With EM31 and/or EM38, optimized operating modes and interpretation models were set up for measuring and assessing groundwater salinity of coastal land in Jiangsu Province. The results show that this new technique has high accuracy, high efficiency and low cost, in exploring groundwater salinity. This research and its results will bring out instructive academic and technique support in the field of mineralized groundwater management and utilization not only in coastal land, but also in inner dry farming and irrigation areas with shallow groundwater table.