Numerous studies Have shown that limb ischemic preconditioning can protect vital organs (including the heart) from ischemia-reperfusion injury,which has a broad application prospect.But its mechanism is still unclear. Evidence showed that humoral mechanisms may play an important role. This study was carried out on the limb ischemic preconditioning in healthy volunteers, collected their serum at different time points before and after treatment,classified and identified the serum proteins during different periods of limb ischemic preconditioning,by using methods including high abundant protein removal,Two-dimensional electrophoresis chromatography and mass spectrometry,then analysed activation and synthesis of the proteins in order to search for the proteins or peptides whose synthesis was activated by ischemic preconditioning. This study will be the first systemic explore of the changes in serum proteins of limb ischemic preconditioning in human body,and lay theoretical basis for the clinical application of limb ischemic preconditioning and for further explore of its humoral mechanism,thus provide clues for searching for protein or peptide having protective effects for organs.