Abstract: Charpy impact test of 16MnR was carried out in 20 ℃~-55 ℃, the fracture process was detected by acoustic emission technology, and the impact fracture was analyzed by metallography and SEM. The results showed that the AE count rate, energy and duration showed decreasing trend when temperature decreased, but amplitude changed little. The d2 energy of wavelet decomposition contained the mainly impact crack energy, and the same trend was found with impact energy. In this text, wavelet analysis and Fourier transform are used to ensure the spectrum characteristics and voltage value generated in crack of 16MnR samples, and thus providing a way for quantitative detecting internal structure change of material under impact load.