Abstract: Lock-in amplifier technology can extract weak signal amplitude with fixed frequency from the strong background noise, thus it has been widely used in scientific research and industry. In this paper, based on the basic principle of lock-in technology, we simulate the extraction of a pulse signal with a certain repetition rate from the strong background noise, study the limitation performance, and investigate the parameters that affect the performance, including the integration time, the pulse width, and the noise types, etc. The simulation results show that the detection limitation of lock-in technology is −60.04 dB from the uniform noise environment and −54.29 dB from the white noise environment. These results will offer a theoretical reference for the preliminary use of lock-in technology to extract weak signal, help to estimate its work states and signal-to-noise ratio.