Abstract: ATF3(activating transcription factor 3)is a stress-inducible protein that increases rapidly after signal stimulation to maintain celluar homeostasis by regulating the expression of its target genes.Therefore,ATF3 has been associated with multiple diseases.However,the role of ATF3 in normal tissues is still less known.To probe the ATF3 expression in unstimulated mouse brain,the RT-PCR,Realtime PCR,Western blot and IHC experiments were performed to detect the ATF3 expression. Both mRNA and protein of ATF3 was detected in frontal lobe,parietal lobe,occipital lobe,temporal lobe,thalamus,opisthencephalon and hippocampus of all unstimulated mice,no statistic difference was found across the different regions of the mouse brain.The results demonstrated that ATF3 can stably express in mouse brain under normal physiological process,indicating it functions in normal unstilumated mouse brain.