Objective　To examine whether ischemia preconditioning (IPC) can decrease ischemia reperfusion(I/R) injury in retina and investigate the mechanism. Methods　Retinal ischemia was induced in SD rats by increasing the intraocular pressure to 14.63kPa for 60 minutes via cannulation into the anterior chamber. Retinal ischemia for 5 minutes constituted the preconditioning stimulus. Rats first underwent IPC and 60 minutes of ische- mia 30 minutes, 24 or 72 hours later or they underwent a 5-minute sham PC and 60 minutes of ischemia 24 hours later. Their electroretinography(ERG), Light microscopy(LM),transmission electron microscopy (EM) and the expression of heat shock protein 70(HSP70) were observed and the content of malandialdehyde(MDA) in rat retinas were measured 24 or 72 hours later after 60 minutes ischemia.Results　Ischemia induced histologic damage was completely prevented when IPC was performed 24 or 72 hours (but not 30 minutes) before ischemia. In contrast to the sham PC group, the amplitudes had complete recovery of b-waves with preischemia basline amplitudes (P<0.01),and the content of MDA was significantly decreased (P<0.01).Conclusion　IPC provides protection against retinal I/R injury just during limited period of time.