Grasslands typical but different in salinity-alkalinity in the Songnen Plain were selected to study conductivity, ion composition, carbon characteristics and microbial composition of the soils. Results showed that soils in the three different regions varied significantly in physico-chemical characteristics and microbial composition, and that soil structure and microbial communities also varied with the process of salinization of the saline-alkaline soils. It can be concluded that grasslands of the Songnen Plain is a fragile kind of ecosystem that calls for intensive protection and management.