The proteins which bound with lipid layers were named membrane proteins in biomem-brane.Because of the large hydrophobic surface in membrane proteins, and the amphiphilic (hydrophobic and hydrophilic) character,their purification and crystallization are very difficult.Introducing small molecular detergent and small amphiphil into crystallization system of membrane protein,a great progress have been made. So far,a few membrane proteins have been crystallized, among them only the reaction center of Rhodopseudomonas viridis and Rhodopseudomonas sphaeroides have produced crystals and been analysed with 3Å resolution. Two-dimensional crystal can be formed in a series of membrane proteins and the information of three-dimensional structure may be obtained by electronmicroscopy and image reconstruction.