Objective：To investigate the mechanism for decrease of glucocorticoid receptor mRNA (GR mRNA) during heat shock response. Methods: The changes of GR mRNA level in SMMC-7721 cells were examined by semi-quantitative RT-PCR during heat shock response. We designed 2 RNA fragments paired with GR gene intron E and cross exon 3, 4, and 5, which were used as probes for in situ hybridization with the sequences in SMMC-7721 cells at different periods after heat shock. The result was subjected to confocol microscope observation and computer image analysis. The transcription, degradation, and splicing of GR mRNA were investigated. Results: RT-PCR showed that the GR mRNA level was decreased during heat shock response. In situ hybridization revealed that both GR mRNA and GR pre-mRNA levels were lower in the heat shock group than in the non-heat shock group(P<0.05). GR pre-mRNA level was higher in cells treated with actinomycine D before heat shock than in cells only treated with actinomycine D, while the GR mRNA level was lower in cells treated with actinomycine D before heat shock(P<0.05). Conclusion: During heat shock response, GR mRNA transcription is suppressed, the splicing of GR pre-mRNA is suppressed, and GR mRNA degradation is accelerated.