The soil of herbaceous plant communities associated with Tamarix chinensis forests of similar density in the coastal tidal flat of the Yellow River Delta was selected as the study object. The study involved the measurement and analysis of various parameters, including pH, electric conductivity, salinity, nutrient content, as well as α- and β-diversity indices of herbaceous plant communities. To quantitatively assess the effectiveness of different herbaceous plant communities in ameliorating saline soils, the fuzzy membership function method was utilized. This approach also facilitated the analysis of the roles and contributions of various factors in the improvement of coastal saline-alkali soils. The findings revealed that the establishment of diverse herbaceous plant communities beneath the coastal T. chinensis shelter forests in the Yellow River Delta significantly contributed to the reduction of soil salinity, mitigation of soil alkalization, and enhancement of soil nutrient content. Moreover, the analysis reveals that there are statistically significant differences in the improvement effects exerted by various herbaceous plant communities on saline soils, as indicated by a P-value of less than 0.05. These results underscore the importance of selecting appropriate herbaceous plant species for the effective rehabilitation of saline-alkali soils in coastal regions. The herbaceous plant community dominated by Phragmites australis performs best in suppressing salt, fertilizing, and preventing alkalization. The examination of diversity indices within plant communities indicates that the richness of species and the diversity indices exert a more significant influence on the enhancement of soil quality. The investigation into the chemical properties of the soil further illustrates that various herbaceous plant communities possess distinct ecological roles in the amelioration of saline soils. Specifically, the community dominated by Oxybasis glauca shows the most favorable outcomes in terms of diminishing soil salinity and augmenting the levels of available nitrogen. When it comes to the enrichment of total phosphorus in the soil, the community of P. australis proves to be the most efficacious. Moreover, for the improvement of total potassium, available phosphorus, and available potassium in the soil, the community led by Suaeda salsa achieves the most superior results. In the context of establishing T. chinensis shelter forests along the coastal regions of the Yellow River Delta, it is advisable to prioritize the selection of the herbaceous plant community dominated by P. australis, which should be integrated with other species such as Suaeda glauca, O. glauca, Cynanchum chinense, S. salsa, and Setaria viridis to optimize the ecological benefits and soil improvement outcomes.