Wavelet-based denoising methods have been successfully applied in processing images with high-frequency noise, such as salt noise, Gausian noise, Poisson noise, etc. However, it is less effective when processing images with low-frequency noise. Seemingly, we can consider using high-pass filter directly to remove the low-frequency noise, but it turns out that when the noise is removed, the useful low-frequency information is also weakened during the process. In this paper, we proposed a new approach to denoise the images with low-frequency noise via pre-emphasis and high-pass filtration. Thereby we removed the low-frequency noise effectively without losing useful low-frequency information. The approach can be well applied in decreasing the interference of low-frequency noise in image transmission.