Saline area is an important reserve resource of arable land, however, the effects of soil microorganisms on the soil fertility in saline coastal ecosystems remain poorly understood.  The salinity effects on soil microorganisms, nutrient availabilities and their relationships were studied in soils along a salinity gradient.  A total of 80 soil samples were collected from 16 sites at four salinity levels (non-saline soil, salt content<1 g kg^–1; low salinity soil, salt content=1–2 g kg^–1; middle salinity soil, salt content=2–4 g kg–1; high salinity soil, salt content>4 g kg^–1).  The results showed that the salinity increased soil pH and exchangeable Na percent, but decreased soil organic matter, soil exchangeable K, and soil microbial biomass.  Both the abundance and community composition of soil bacteria and fungi were significantly different between the non-saline and the saline soils.  The predominant genera of soil bacteria (Planctomyces and Archangium, positive for carbon fixation) and fungi (Hydropisphaera, efficient in lignin degradation) changed with the increasing soil salinity and the decreasing soil organic matter.  In summary, soil salinity changed the abundances of soil bacterial, fungal, and arbuscular mycorrhizal communities and, subsequently, affected their function in saline coastal ecosystems.