【Objective】The wilt coefficient is a key factor in determining the effective soil water range, reserves and availability to plants. However, the existing wilting coefficient based on plant morphological changes has the disadvantages of unclear physiological significance and is difficult to determine in the field. 【Method】To this end, in this study a pot experiment under dry-down drought was used to determine the wilting coefficients of 4 plant seedlings (Glycine max L., Helianthus annuus L., Medicago sativa L., and Leymus chinensis (Trin.) Tzvel) grown under two soil textures (loessial soil in the Loess Plateau and red soil in the southern hilly area). We evaluated the dynamic response of leaf gas exchange parameters to changes in soil moisture content, the relationship between the lower threshold of soil moisture determined based on plant gas exchange parameters, and the wilting coefficient. 【Result】The results showed that: (1) Soil texture and plant drought resistance significantly affected the wilting coefficient of plants and the corresponding soil water potential at permanent wilting. The wilting coefficients of all four plants were greater on the red soil than on loessial soil. Importantly, the stronger the drought resistance of a plant, the lower its wilting coefficient. The wilting coefficients of the four plants under loessial soil were 0.083 cm³·cm^-3(Helianthus annuus L.)> 0.081 cm³·cm^-3(Glycine max L.)> 0.072 cm³·cm^-3(Leymus chinensis (Trin.) Tzvel) > 0.060 cm³·cm^-3(Medicago sativa L.). Also, the wilting coefficients under red soil were 0.188 cm³·cm^-3(Helianthus annuus L.)> 0.180 cm³·cm ^-3(Glycine max L.)> 0.174 cm³·cm^-3(Leymus chinensis (Trin.) Tzvel) > 0.172 cm³·cm^-3(Medicago sativa L.). (2) The soil moisture lower threshold determined by using a cubic function to simulate the change of stomatal conductance was highly consistent with the measured wilting coefficient.【Conclusion】Thus, the wilting coefficient could be estimated indirectly based on plant gas exchange parameters.