Abstract: The aim of the present research is to develop a model for an accurate estimation of herbaceous plant biomass. The biomass of Spartina alterniflora in Yellow River Delta was calculated with regression model based on the relationship between measured biomass and morphological parameters, which include height, density and stem diameter. The results indicated that the aboveground biomass and total biomass were positively correlated to height, density and stem diameter (p<0.01). The underground biomass was positively correlated the plant density (p<0.01). The regression models between biomass and plant morphological parameters were compared and it resulted that the growth curve of aboveground biomass with height (R²=0.904) and the total biomass with density (R²=0.659) were the best fit models with optimal goodness. The application accuracy evaluation showed that the absolute error ranges of the measured and calculated biomass are 0.01-0.17 kg/m² and the relative errors are 0.71%-12.02%. Based on the estimation and verification, it was found that the regression models could be used to evaluate accurately the cordgrass biomass with parameters such as density and stem diameter.