Abstract: This article analyzes the cause of desert enlargement and sums up the researches of some predecessors.On the basis of forming desert soil processes,of which the first is soil granularity changing coarse grain,the second is underground water level rising,an effective measure is put forward to harness desertification by way of increasing soil's viscidity,improving soil's quality and preventing evaporation and leakage.The experiment,based on the rule that organic-inorganic compounds produce glue after combining with Ca²⁺ in soil and then the glue will obstruct capillary and increase soil's viscidity while decrease evaporation,adopts imitate soil-column method.This glue is called water-preventing membrane.This measure is proved to be effective in harnessing desert enlargement and in increasing soil density and in decreasing soil evaporation.This glue contents PAA.Different PAA neutralization density and different pH of emulsion can produce water-preserving membrane with varied quantity and in function of decreasing soil evaporation and preventing soil leakage.Therefore on the basis of different soil that has different vadose coefficient,different PAA neutralization density and different pH of emulsion being used can produce good results of improving the desert soil.Germination experiment show s that this measure does not harm and poison the crops and o n the contrary promotes crops germination and growing.This measure has a bright future in harnessing desert enlargement.

Key words: water-saving technique, gelation, arid and semi-arid regions, sandy soil