This paper was designed to investigate the expression of p53, p21of A549 cell strains under hypoxic condition and the effect of trichostatin A (TSA), the inhibitor of histone deacetylase1 (HDAC1) on their expression. The authors designed 1 normoxia group (control group) and 6 hypoxia groups (experiemntal group): hypoxia 6 h group (A), TSA+ hypoxia 6 h (B), hypoxia 12 h group (C) ,hypoxia 24 h group (D), TSA+hypoxia 24 h (E), hypoxia 48 h group (F). The expression of HDAC1 in A549 cells was examined by using Western blot and the expression of p53, p21 in A549 cells and the effect of TSA on them were determined by using immunohistochemistry and reverse transcription polymerase chain reaction (RT PCR). The A value expressed by HDAC1 in A549 cell strains was 138±11 in the control group, 78±4, 86±5, 124±3, 120±9 in experimental groups A, C, D, F, respectively. The A value of the expression of the protein and mRNA of p53 in A549 cell strains were 0.12±0.02, 0.62±0.02 in the control group, 0.10±0.03, 0.32±0.03; 0.11±0.01, 0.33±0.02; 0.13±0.03, 0.58±0.01; 0.12±0.02, 0.56±0.02 in experimental group A, B, D, E, respectively. The A value of the expression of the protein and mRNA of p21 in A549 cell strains were 0.17±0.03, 0.62±0.03 in the control group, 0.16±0.02, 0.50±0.02; 0.14±0.02, 0.36±0.02; 0.15±0.03, 0.49±0.03; 0.13±0.02, 0.33±0.02 in experimental groups A, B, D, E, respectively. These results indicate that the expression of HDAC1 is regulated by hypoxia and the effect of TSA is closely related to the expression of P21 under hypoxia condition. This paper was designed to investigate the expression of p53, p21 of A549 cell strains under hypoxic condition and the effect of trichostatin A (TSA), the inhibitor of histone deacetylase 1 (HDAC1) on their expression. The authors designed 1 normoxia group (control group) hypoxia 6 h group, hypoxia 6 h group, hypoxia 12 h group, hypoxia 24 h group, TSA + hypoxia 24 h group, hypoxia 48 h group (F). The expression of HDAC1 in A549 cells was examined by using Western blot and the expression of p53, p21 in A549 cells and the effect of TSA on them were determined by using immunohistochemistry and reverse transcription polymerase chain reaction ( RT PCR). The A value expressed by HDAC1 in A549 cell strains was 138 ± 11 in the control group, 78 ± 4, 86 ± 5, 124 ± 3, 120 ± 9 in experimental groups A, C, D, F, respectively The A value of the expression of the protein and mRNA of p53 in A549 cells were 0.12 ± 0.02, 0.62 ± 0.02 in the control group, 0.10 ± 0.03, 0.32 ± 0.03; 0.11 ± 0.01, 0.33 ± 0.02; 0.13 ± 0.03, 0.58 ± 0.01; 0.12 ± 0.02, 0.56 ± 0.02 in experimental group A, B, D, E, respectively. The A value of the expression of the protein and mRNA of p21 in A549 cells were 0.17 ± 0.03, 0.62 ± 0.03 in the control group, 0.16 ± 0.02, 0.50 ± 0.02; 0.14 ± 0.02, 0.36 ± 0.02; 0.15 ± 0.03, 0.49 ± 0.03 ; 0.13 ± 0.02, 0.33 ± 0.02 in experimental groups A, B, D, E, respectively. These results indicate that the expression of HDAC1 is regulated by hypoxia and the effect of TSA is closely related to the expression of P21 under hypoxia condition.