Abstract: During laser strengthening mould surface,the fluctuation of defocusing amount was caused by clamping and teaching errors,which greatly influenced the quality of laser strengthened mould surface.Thus,Hilbert-Huang Transform (HHT) analysis of acoustic signal characteristics caused by the fluctuation of defocusing amount on laser strengthened mould surface was put forward.According to the acoustic signal characteristics of laser strengthened mould surface,the HHT analysis steps were proposed.The mould life was improved over 20% when the mould surface was strengthened by the HHT analysis system.The experimental results provide a method for further researching and using laser strengthening acoustic signal.