Dialdehyde starch (DAS) is a kind of starch derivative,and in possession of some excellent function of physical chemistry and biochemistry for the presence of lots of aldehyde groups,so it is of widely use in fields of food and medicine.In this study,dialdehyde starch nanoparticles (DASNP) were prepared with redox and nanotechnology in the reversing microemulsion-crosslinking system:starch solution was put into the oil phase (toluene/chloroform =3/1),and mixed for a certain time to form microemulsion; 0.01% POCl3 was added and mixed for 40 min,then some quantity of sodium periodate (NalO4) was added to the reactive system and mixed for lh; in the end,the microemulsion was washed three times with acetone and ethanol respectively.