Abstract: The AE technique was used to monitor the box beam with external crack on the crane during the three-point bending test. The characteristics of AE signals with crack propagating were analyzed. The parametric characteristics of the location sources were compared on the different load level in the test. The research proved that the signals of the crack propagating were burst emission with its amplitude distribute being from 45 to 60 dB mainly and frequency domain being from 100 to 450 kHz. The results indicated that the linear location method could be used well for the AE sources location of box beam when the external crack was propagated during the three-point bending test.