Applying Wall tapping and roof sounding for coal blasting mining, excavation face to determine whether the status of roadway roof separation occurs. Firstly through beating the different parts of rock layers and record the received voice signal, which do the DTW feature extraction of the voice signal. Secondly based on the model database of constructed roof separated layer, determining the state of the roof combining with BP neural network recognition algorithm, after the extraction of DTW feature and the sequence data generated. Finally simulation and experiments show that identification method based on DTW, determining the state of the roof characteristic. Whether the roof separation of roadway occurs, to avoid the misjudgment problems of lack of experience in practical works.