Accurate recognition and mechanism analysis on spatial distribution of soil salinity are of great significance for scientific utilization of saline-alkali land.To solve the problems of heavy workload, poor representativeness and high detection cost from the conventional method, this study used the electromagnetic instrument to assess the spatial distribution of soil salinity in a typical farm in Chongming coastal area, Shanghai, so as to provide guidance for agricultural production as well as scientific and accurate improvement according to the salinity classification and salinization mechanism.The results showed that there was a significant positive linear correlation between the apparent electrical conductivity (EC_a) and soil salt content (R²>0.9, P < 0.05), indicating that EC_a would be used to characterize the variation of soil salinity.The spatial distribution and variation of soil salinity in the area was obtained by Kriging interpolation, and found that the spatial distribution of soil salinity was not uniform, and nearly 80% of the areas was with mild to moderate salinization.The evaluation of soil salinity profiles by spot sampling showed that soil salinity in this area was with a strong surface aggregation and spatial variation, and the coefficient of variation decreased with the increase of soil depth.Correlation analysis of interpreted soil salinity, soil pH, organic matter content, and major constituent ion content was conducted to dissect salinization types and formation mechanisms.The main salinization in this area was sulfate type, and the influences of seawater infiltration and groundwater re-salinity were the main reasons for the formation of salinization.The study provides a rapid, large-scale, scientific and dynamic monitoring for soil salinization, which is of great significance in promoting the utilization technology and realizing the efficient and sustainable utilization of saline-alkali land.