As a non-destructive and real-time detection technology, acoustic emission (AE) testing has been widely applied in the state prediction and fault diagnosis in wire electrical discharge machining (WEDM). However, there has been limited research investigating the sources of interference affecting AE signals during the machining process. These sources of interference can induce noise, resulting in AE signals distortion. Therefore, this study designs a filtering algorithm based on discrete wavelet transform (DWT) to reduce the impact of noise on the AE signals. The experimental results indicate that noise mainly resides within the frequency ranges of [500,000Hz, 1,000,000Hz] and [0Hz, 15,600Hz], while AE signals generated by the workpiece are primarily distributed in the range of [32,300Hz, 500,000Hz]. The signal-to-noise ratio (SNR) of the filtered AE signal is 10.7dB, which is beneficial to analyze and extract features of signals in the follow-on work.