Three suborder soils in southwest China were adopted,namely Ustic Vertisol,Stagnic Anthrosol and Ustic Ferrosol, so as to carry out the basic physical and chemical analysis respectively, to design a dynamic measuring method for water stability of soil structure and conduct the comparative study on the quality of the soil structure. The results indicated that ① The water stability dynamic characteristic of the soil structure could well reflect the maintaining capability of the soil structure as time goes on. ② The quality of several soil structures in southwest China was sequenced as follows:Stagnic Anthrosols ∨Ustic Vertisols ∨Ustic Ferrosols. ③ The water stability of soil structure is very positively correlated with the capillary porosity and the clay particle (D ∧0.002 mm) content (Cc), but is very negatively correlated with the silt (D is 0.05-0.002 mm) content (Csc), and ④ The dynamic functional equation of the water stability of soil structure in southwest China was established, so that the water stability characteristics of various soil structures could be quantitatively expressed and the quality of different soil structures can be quantitatively compared from each other. Three suborder soils in southwest China were adopted, namely Ustic Vertisol, Stagnic Anthrosol and Ustic Ferrosol, so as to carry out the basic physical and chemical analysis respectively, to design a dynamic measuring method for water stability of soil structure and conduct the comparative study on the quality of the soil structure. The results indicated that ① The water stability dynamic characteristic of the soil structure could well reflect the maintain capability of the soil structure as time goes on. ② The quality of several soil structures in southwest China was sequenced as follows : Stagnic Anthrosols ∨ Ustic Vertisols ∨ Ustic Ferrosols. ③ The water stability of soil structure is very positively correlated with the capillary porosity and the clay particle (D ∧ 0.002 mm) content (Cc), but is very negatively correlated with the silt (D is 0.05-0.002 mm) content (Csc), and ④ The dynamic functional equation of the water stability of soil structure in southwest China was established, so that the water stability characteristics of various soil structures could be quantitatively expressed and the quality of different soil structures can be quantitatively compared from each other.