Abstract: A study on the membrane components of rat hippocampus was presented. The isoelectric focusing OFFGEL combing with the reversed-phase liquid chromatography and mass spectrometry was adopted as the major tool to study the separation and enrichment capability of tryptic peptides. The database for annotation, visualization and integrated discovery(DAVID) was used to analyze the acidic proteins which were separated based on GO (gene ontology). The results indicate that there are 24 different fractions, each of which is identified by nano-reversed-phase liquid chromatography coupled with quadruple tandem time-of-flight mass spectropho-tometer (Q-TOF). About 77% of the identified peptides are found in only one fraction. Moreover, little deviations are observed at low pH value and it has a good focusing effect.