Abstract: The safety of rail is very important for the development of high speed railway, and it is necessary to investigate the features of inside defects in rail. In order to obtain the features of Acoustic Emission (AE) sources of inside defects in rail, AE sources with different types, depths and propagation distances are examined for rail defect detection. The finite element method is utilized to model the rail with defects and the results of experiment demonstrate the effectiveness of this model. Wavelet transform and Rayleigh-Lamb equations are utilized to extract the features of AE sources. The results of this study clearly illustrate that the interrelationship among AE modes possesses a distinctive feature to identify the AE source types and the AE sources with different frequencies in rail. There are uniform AE mode features existing in the AE signals from AE sources in rail web, however AE signals from AE sources in rail head and rail base have the complex and unstable AE modes. Different AE source types have the different propagation features in rail. It is helpful to understand the rail defects and detect the rail defects based on the AE technique.