In the machining process of iron tower, the angle steel needs to be operated through clamping, punching, shearing, etc, and different material produces different sound, so it is advised to use sound signal to detect steel materials Q235 and Q345. Experiment system is constructed by using the sound sensor and signal acquisition system, so the continuous sound signal is acquired, and the sound wave of single punching cycle is exacted for the follow-up judgement. For the sound signal in one cycle, MFCC(Mel Frequency Cepstrum Coefficient) parameters are extracted as characteristic parameters, and the distances between the being measured template and the two standard templates of Q235 and Q345 are computed by the DTW (Dynamic Time Warping) method. As a result, which distance is smaller determines the template. In the experiment, two sets of samples for four kinds of angle steels are acquired, respectively, which proves the validity of the method for steel material detection.