In order to solve the problem that the high voltage cable insulation monitoring system collects the noise of the partial discharge pulse signal in the actual working environment, this paper presents an EMD denoising algorithm based on ICA. The principle of denoising of the algorithm is introduced in detail. The advantage of the algorithm is that it not only effectively removes the noise in the PD signal but also retains the integrity of the PD signal well. After laboratory simulation experiments and on-site monitoring of on-line insulation, we can see from the experimental results that the algorithm has a good effect of denoising, which proves the effectiveness and reliability of the algorithm. This work is supported by Henan Joint Project of National Natural Science Foundation of China (No. U1404522).