Under alkaline conditions,the aldehyde group is introduced into dibenzo?18?crown?6 (DB18C6) with the help of chloroform (CHCl₃) to prepare dimethyl dibenzo?18?crown?6 (DDB18C6).Then,using DDB18C6 and soluble deacetylated chitin (CTS) as raw materials,Schiff reaction was used to synthesize a grafted crown ether CTS membrane with an increasing mass fraction of small molecule crown ethers,which was named C _a ?CTS membrane (a=m(DDB18C6)/m(C _a ?CTS membrane）).The C _a ?CTS membrane is ion exchanged in alkali solution.The C _a ?CTS membrane absorbs K⁺ through the oxygen hole structure,and then the C _a ?CTSK membrane is prepared.Eeach stage the sample membrane was subjected to structural characterization and performance testing.The results show that with the increase of the crown ether grafting degree,the thermal stability of CTS can be improved;when a=0.20,the grafting degree of C_0.20?CTSK membrane can reach 43.91%,the water absorption rate can reach 168.6%,the IEC value is 1.38 mmol/g. At a temperature of 70 ℃,the conductivity of C_0.20?CTSK membrane can reach 46.8 mS/cm; the introduction of grafting of crown ether improves the alkali resistance stability of this series of membranes. After the C _a ?CTSK series membranes are soaked in 6 mol/L KOH solution for 480 hours, the conductivity decreases only 4.0%.