Abstract: In order to meet the requirements of eggshell crack detection for on-line application, an automatic knocking device was designed, which can make an impact on eggshell without any damage and collect the vibration signal from the egg surface through a microphone placed in the center of the automatic knocking device during the exciting time. The structure and working principle of the device, operating parameters and software working flow were introduced in the paper. And the experiment of vibration signal collecting on eggs was carried out. The test results show that the system runs steadily and reacts swiftly, the accuracy ratio of knocking can reach 100%, and the mechanical impact was so moderate that there would not be any new crack on eggshell. It should be highlighted that the microphone can record the real time signals clearly.