Abstract: In order to provide a better understanding of the theoretical basis of soil improvement, The author showed the relationship with soil structure, soil clay, soil salinity,total soil porosity and different suction conditions. It introduced the methods and principles on improving water storage capacity (soil tillage and straw mulch, soil stirring, aquasorb). And then it assessed the effect of different method according to the former research. Finally, the author sumed up 3 analysis methods of soil: specific water capacity method, regression coefficients method, percentage cumulative water loss method.