Abstract: The theoretic model: there are three interfaces before the tunnel face,the medium between any adjacent interfaces is homogeneous and the wave velocity in one layer of medium may be different from ones in the others.We studied the methods of forecasting,layer by layer,and reversed the arrival time of wave which deduced by the known interfaces and wave velocities to the interfaces. Results are almost concordant with the fact.To the tunnel model and Yuntai Mountain tunnel face, we recorded waveforms respectively by ultrasonic detector and seismic detector. By analysis of severel of waves on record, we obtained the data on the arrival time of the reflection wave, and then reversed the data to the interfaces.The results are in good agreement the true conditions.

Key words: tomography, method of calculation