The work aims to propose an online detection method of laser shock peening based on shock wave signal energy in air to overcome the existing disadvantages of offline laser shock peening detection methods. The TC16 titanium alloy samples after the treatment of vibration stress relief were treated by Nd:YAG laser with a wavelength of 1064 nm, pulse width of 14 ns and pulse energy of 5~7 J. The shock wave signals in air were first amplified by the signal amplifier that independently developed by our research group, then transmitted to the computer control system through the preamplifier and the data acquisition card successively. So the sampling, storage, filtering and data analysis of shock wave signals in air were realized, then the shock wave signal energy was extracted. The surface residual stress of TC16 titanium alloy samples after the treatment of laser shock peening were measured by the X-350A X-ray stress tester. Finally, according to the obtained experimental data, an empirical formula between the surface residual stress of the material and the shock wave signal energy was obtained by polynomial fitting. The experimental results shown that after treatment of laser shock peening, there are a certain amount of residual compressive stress was formed on the surface of the material. At the same time, both the surface residual stress and shock wave signal energy were increased with the increases of laser energy, and their growth trends are consistent. In conclusion, during the process of laser shock peening, by collecting the shock wave signals propagating in air and extracting the shock wave signal energy, the residual stress of materials can be predicted and the quality of laser shock peening can be judged accurately, which will realize the online control of industrial process.