The linear attenuation coefficient (mu) is an important coefficient in the study of diagnostic radiology. The mu values of dentin and enamel were rarely reported because they are thin and tightly connected to each other and are difficult to measure by thermoluminescent dosimeters or ion chambers. In this work, we used film densitometry to measure the radiation dose before and after they transmitted the 2 mm thickness tooth slice and used this data to calculate the mu values of enamel and dentin. The results show that the mu values of enamel at 70, 80, 90kVp are 2.97 +/- 0.71, 2.85 +/- 0.07, 2.70 +/- 0.16 cm-1, respectively. The mu values of dentin at 70, 80, 90kVp are 2.12 +/- 0.92, 1.81 +/- 0.23, 1.89 +/- 0.42 cm-1, respectively. The mu values may be affected by the equivalent energy of an x-ray generator operated under different kVp conditions and also by the density and calcification degree of the enamel and dentin. Nevertheless, the results obtained in this study still can severe as a reference for researchers.