Aiming at the problem of noise in the traffic monitoring, especially at night, an image denoising algorithm is proposed. Application of correlation denoising algorithm based on wavelet transform in traffic monitoring. Firstly, Haar wavelet is used as the transform matrix, then image data are denoised. And The similarity of the image is evaluated by the peak signal to noise ratio. Finally, the obtained data is compared with the algorithm of existing adaptive threshold. It is found that the improved algorithm of correlation denoising achieved the expected effect and can denoise the monitoring image of nighttime very well.