Objective: To investigate the expression of heat shock protein 70 in dental pulp tissue after cavity preparation. Methods: The expression of inductive heat shock protein 70 mRNA and hybridization allocation were detected in dental pulp tissues with deep cavity, shallow cavity, and no cavity. Results: The heat shock protein 70 mRNA expression in the shallow cavity and no cavity groups were negative, while those in the deep cavity group were positive with omnipresent staining on odontoblasts, fibroblasts, endothelial cells, and vascular smooth muscle cells. Conclusion: These results suggest that heat shock protein 70 may help to relieve dental pulp injury caused by exogenous factors and may maintain the normal function of dental pulp cells. The inductive heat shock protein 70 expression may have a threshold that can be used as an index to investigate the correlation between heat shock protein 70 expression and the depth of drilling. In turn, this may help to direct clinic operations.