The study on protection of grounding grids from corrosion in soil is of great significance to safe operation of power networks Soil samples were collected from the grounding grid sites of 21 transformer substations in Cangzhou region as research objects Corrosive factors in the soil samples were determined and measured on the spots and in the lab,and the data were analyzed using the principal component analysis method for statistics Results show that chloride,total salinity and electrical resisti vity were the key corrosive factors in grounding grid soils Based on the indexes of chloride content and total salinity in the soil,the soil samples were sorted into three groups:coastal moderate/severely salinized soil,slightly salinized fluvo aquic soil and flu vo aquic soil When key corrosive factors and soil types were cited as evaluation indexes,corrosiveness of the soil samples was divided into three grades,that is,very strong,strong and moderate The Gangcheng Transformer Station and 3 others in the coastal region stand in soils,very strong in corrosiveness,the Liliubao station and 9 others in soils,strong in corrosiveness,and the Hancun station and 8 others in soils,moderate in corrosiveness.