Super Absorbent Polymer (SAP) is one kind of polymer with function of strong water absorbent and conservation.It has been paid attention to application in agricultural production, soil & water conservation and the pollution management in recent years.SAP is synthesized by natural hydrophilic monocase with cosslinking agent and initiator; there are three kinds of reaction type, such as graft copolymerization, carboxymethyl reaction and crosslinking reaction.Based on the raw material and synthetics techniques, the type of SAP can be divided into organic monocase polymer(such as Sodium Polyacrylate), starch polymer(such as starch graft acrylic acid sodium), organic-inorganic compound polymer (such as Bump/sodium polyacrylate) and organic monocase and functional component polymer(such as humic acid polymer).In order to summarize the new achievement of SAP research and analysis the development direction, based on authors' research accumulation and the literature's review, the paper reviews SAP development history, and summarizes the acting principle system of SAP, including five aspects.First is the principle of water absorbing, retaining and releasing of SAP itself.SAP can absorb deionized water 400~600 times or tap water 100 time of itself weight by method of water absorption and the swelling, and more than 85% water can be used by plants.Second is the principle of SAP improving soil and water conservation.SAP can improve the soil aggregate structure, increase the soil porosity and water infiltration, and reduce the evaporation of soil surface.Third is the principle of effect on SAP raising the use ratio of fertilizer, pesticide and other chemical materials.On fertilizer conservation and the use efficiency, SAP has the function on controlling nitrogen release and increasing the phosphorus release in soil.The key rule of SAP is major on reducing the rate of nitrogen release owing to nitrogen ions exchanged with functional groups of SAP and soil, the effect is stronger with increasing of SAP amount in soil.Meanwhile, SAP can increase the release rate of phosphorus fertilizer owing to the activating of soil phosphates.Fourth is the principle of effect on SAP raising water use efficiency by adjusting the plant physiological function to raise water use efficiency.This is related with SAP use way, in normal SAP is used in pot or furrow, this way can supply water directly for part root of plants, and other part root is in drought that can make plant root produce hormone ABA, and which can be moved to leaf to adjust stomata optimally for water use efficiency.Fifth is the principle of SAP effect on soil heavy metal immobilization.Heavy metal pollution in soil is a very serious problem in farmland environmental protection in China, especially Cd and Pb compound pollution.The experimental certificated that SAP and the compound materials can decrease over 50% heavy metal Pb and 80% Cd absorbent by maize in soil, and also immobilized over 69% Pb and 33% Cd absorbent by soybean in soil.On the other hands, the paper also analyzes the research development in agricultural production, vegetation construction, soil & water conservation and the pollution management, especially on water and fertilizer conservation and the high efficiency use, heavy metal pollution management of soil, etc.According to the exiting problems and practice production requirement, the development direction of SAP is to enhance the develop new type of SAP, strengthen the application basic research and the extensive technology transfer in future.