Acoustic emission（AE）technology was used to monitor the corrosion process of steel bars by using the accelerated corrosion method of dry and wet cycles. The aim of test was to study AE signal characteristics of steel bars in the process of corrosion in cement based materials. The results show that the mortar is accompanied by a large number of AE signals during the curing process,and the peak frequency is mainly concentrated in two frequency bands of 2060kHz and 130200kHz.The cement based materials are accompanied by AE signals in the process of water absorption and dehydration, and the peak frequency of AE signals is about 50kHz. By using the statistical analysis of AE signal energy distribution and b value method, it can accurately determine the occurrence of steel bar corrosion in cement based materials.The peak frequency range of AE signal corresponding to the rupture of passivation film of steel bars is 100150kHz, while that to pitting is concentrated at 2070kHz.