Objective To investigate the effect and mechanism of mitochondrial translocation regulation of translocase of outer mitochondrial membrane 70 (Tom70) /polyribonucleotidyltransferase 1 (PNPT1) in hypoxic injury of rat myocardial cells. Methods (1) Rat H9C2 cardiomyocytes were divided into control group (treated with normoxia for 12 hours) and hypoxia group (treated with hypoxia for 12 hours). The apoptosis rate of cardiomyocytes was detected by flow cytometry, the expression of TUBA mRNA was detected by qPCR, and the expression of PNPT1 protein was detected by Western blotting. (2) H9C2 cells were infected with lentivirus vector carrying Tom70 sequence to up-regulate the expression of Tom70. The cells were then divided into NC group (lentivirus negative control group, containing lentivirus empty vector only), Tom70 over-expression group (lentivirus vector carrying Tom70 sequence), hypoxia+NC group, hypoxia+Tom70 over-expression group. Western blotting was used to detect the expression level of Tom70, PNPT1 protein in cells, and flow cytometry was used to detect the apoptosis rate of hypoxia+NC group and hypoxia+Tom70 over-expression group, the expression of TUBA mRNA in the hypoxia+NC group and hypoxia+Tom70 overexpression group were detected by qPCR, and the interaction between Tom70 and PNPT1 in the cells was detected by immunoprecipitation technique. Results (1) The results of flow cytometry showed that compared with control group, the apoptosis rate of myocardial cells in hypoxic group was significantly higher (P<0.05). The results of qPCR showed that compared with the control group, the content of TUBA mRNA in cells of hypoxia group was significantly decreased (P<0.05). Western blotting showed that compared with control group, the expression level of PNPT1 protein in mitochondria of hypoxic group was significantly decreased, while the expression level of PNPT1 protein in cytoplasm was significantly increased (P<0.05). (2) Western blotting showed that compared with control group and NC group, the expression of Tom70 in the Tom70 over-expression group was significantly increased (P<0.05); Under normal oxygen conditions, there was no significant difference in the expression of mitochondrial PNPT1 and cytoplasmic PNPT1 between NC group and Tom70 over-expression group; Under hypoxia condition, compared with hypoxia+NC group, the expression level of mitochondrial PNPT1 in hypoxia+Tom70 over-expression group was significantly higher, and the expression level of cytoplasmic PNPT1 was significantly lower (P<0.05). The results of immunoprecipitation showed that Tom70 and PNPT1 in cardiomyocytes could bind each other. The results of flow cytometry showed that compared with hypoxia+NC group, the apoptosis rate of hypoxia+Tom70 over-expression group decreased (P<0.05). The results of qPCR showed that compared with hypoxia+NC group, the content of TUBA mRNA in the hypoxia+Tom70 overexpression group increased (P<0.05). Conclusion Tom70 can alleviate hypoxic injury of rat myocardial cells by regulating the expression of PNPT1 mitochondria and reducing the degradation of apoptosis-related mRNA.