Objective High mobility group box-1 protein ( HMGB1) plays an essential role in regulating energy metabolism of tumor cells via affecting mitochondrial autophagy .The aim of this study was to explore the effect of HMGB 1 on mitochondrial biogene-sis and cell energy metabolism in anoxia environment . Methods HepG2 cells were divided into normoxia control group ( cells were cultured in a culture box containing 5%CO2) , hypoxia control group ( cells were cultured in a culture box containing 1%O2+5%CO2+94%N2 ) , hypoxia HMGB1 siRNA group ( cells were cultured in a culture box containing 1% O2+5% CO2+94% N2 after transfected with HMGB1 siRNA) and hypoxia NC siRNA group ( cells were cultured in a culture box containing 1%O2+5%CO2+94%N2 after trans-fected with negative control siRNA ) .MTS assay was carried out to measure cell proliferation rate .The alterations of mitochondrial bio-genesis associated proteins were detected by RT-PCR and western blot.Mitochondrial density and morphology were determined by transmission electron microscopy (TEM).The ATP content in whole cell extracts was determined with a colorimetric ATP detection kit . Results Compared with the hypoxia control and hypoxia NC siR-NA group, the proliferationof hypoxia HMGB1 siRNA group was significantly inhibited, especially in 48 h and 72 h(P<0.05).Com-pared with hypoxia control group and hypoxia NC siRNA group , the expression of PGC 1α, NRF1and TFAM in hypoxia HMGB1 siRNA group were decreased significantly ( P<0.05) .Western blot results showed that , compared with normoxia control group , the expressions of PGC1α(0.494±0.210 vs 0.090±0.020), NRF1(1.080±0.470 vs 0.581±0.190)and TFAM(1.585±0.340 vs 0.792±0.350) protein in hypoxia 24 h group were increased obviously ( P<0.05) .Compared with hypoxia control group and hypoxia NC siRNA group , the expres-sions of PGC 1α, NRF1 and TFAM protein in hypoxia HMGB1 siRNA group were significantly decreased (P<0.05).Compared with hypoxia control group , the content of ATP in the HMGB 1 siRNA hypoxia group was significantly decreased , and hypoxia 12 h and 24 h were the most obvious ( P<0.05) . Conclusion HMGB1 could maintain cell energy metabolism by regulating mitochondrial biogene-sis so that cells could continue to proliferate in adverse anoxia environment .