The method of liquid nitrogen grinding and ultrasonic were applied to crush Nostoc flagelliforme colonies and cells.The crudes were isolated by differential centrifugation;thylakoid membranes were purified by high speed centrifugation with gradient density sucrose;the thylakoid membrane proteins were extracted and separated by SDS-PAGE.The results suggested that:(1)Thylakoid membrane of colonies on dehydration for 6 h(water contenting 51.2%) and on dehydration for 24 h(water contenting 14.9%) were purified by many tims differential centrifugation and then by high speed centrifugation with gradient density sucrose.(2)14 bands of thylakoid membrane protein were separated by SDS-PAGE,their mass weight mainly ranged from 25 kD to 60 kD.8 kinds of protein were identified by MALDI-TOF-TOF/MS and database searching.According to their biological functions,these thylakoid membrane proteins were divided into 4 categories,including photosynthesis proteins(photosystem Ⅱ manganese-stabilizing protein PsbO,F₁F₀ ATP synthase subunit alpha,F₁F₀ ATP synthase subunit beta),binding domain protein(hemerythrin HHE cation binding domain-containing protein),carbohydrate-selective porin(carbohydrate-selective porin OprB),unknown proteins(hypothetical protein Npun_R1321,Npun_R3785 and N9414_02186).They might play an important role in photosynthesis of N.flagelliforme.