Abstract: Application of biological agents to improve saline soil is a relatively fast, economical, simple method with long-term effectiveness. Trichoderma spp. are free-living fungi that are highly active in interaction among root, soil and foliar environments. Biological agents application in agricultural systems is a potential method to ameliorate saline soil, eventually benefiting the environment or ecosystem by regulating soil physical and chemical properties and microbial population. In this study, broadcast granule preparation of Trichoderma agent (containing at least 1×10⁷ colony-forming units of active ingredients for per gram dry weight) was applied to soil of moderately saline coastal platform fields to explore effect of Trichoderma agent on soil properties of moderately saline coastal platform field. Arable layers soils were sampled, which included moderately saline coastal platform field with (T1010) and without (CK) Trichoderma agent under peanut cropping (sandy loam soil with salt content of 2.99 g·kg^-1), flood land in coastal saline area (sandy loam soil with salt content of 26.19 g·kg^-1), reclaimed field in coastal slight saline area under continuous cotton cropping (light loam soil with salt content of 1.75 g·kg^-1), non-saline solar- greenhouse soil under continuous tomato cropping (loam soil with salt content of 0.98 g·kg^-1). All the plot samples were repeated four times, and the physical, chemical and biological properties tested in laboratory. The results showed that Trichoderma agent amended soil physical properties. Compared with CK, T1010 increased soil compaction by 177.04%, content of water stable aggregate of ≥0.25 mm by 265.78%, soil moisture content by 320.83%. In this study, soil chemical properties also changed. The contents of nitrogen, phosphorus, potassium and organic matter increased by 96.14%, 42.17%, 105.65% and 63.79%, respectively, under T1010 compared with those under CK. Under T1010, soil bacteria, actinomyce, fungi and azotobacters amounts increased by 170.95%, 82.68%, 152.17% and 471.93%, respectively, compared with those under CK. Beneficial properties to plants growth (e.g., soil compaction, ≥0.25 mm water stable aggregate, organic matter, microbial amount) of moderately saline coastal platform soils with Trichoderma agent (T1010) increased, respectively, by 1.53, 2.11, 3.20 and 28.33 times over that of flood land in coastal saline area. On the contrary, harmful property to plants growth, water soluble salts, reduced by 96.60%. Properties (such as soil compaction, porosity, moisture, contents of phosphorus and organic matter, and microbial amounts) of Trichoderma-amending moderately saline coastal soils were not significantly different from that of slightly saline coastal alkali soils. Reduced bulk density or increased porosity of moderately coastal saline platform fields with Trichoderma were close to that of the non-saline solar-greenhouse soils. Application of microbiological agents effectively improved soil properties of moderately saline coastal platform fields and ameliorated the ecological environment by enhancing soil aggregate structure, increasing soil nutrient and beneficial microorganisms amount.