Based on the field investigation, as well as the overall background information collection and analysis, the wetland plant communities and environmental factors in Gansu Dunhuang Xihu National Nature Reserve were studied, also the biodiversity index and the environmental factors were compared. The dependent variable y (average coverage) and the independent variable x (soil salinity) were selected based on the multi-variable ANOVA by using SPSS software. The multiple regression fitting model were conducted on the average coverage and the soil salinity in 24 wetland plant communities by using the “Curve Parameter Estimation” method. The results indicated that the logarithmic curvemodel was the best fitting model, and the curve equation was as follow: y=1.076-0.391 lnx(p=0.009). Finally, the deficiency and improvement on this model were put forwarded. This research provided scientific basis on the wetland plant conservation in arid regions of Northwest China.