The objectives of on-line monitoring are to prevent failures, reduce maintenance costs, and predict the life of the power system equipment. It is non-destructive and also cost-effective due to its ability to be applied when the equipments are in-service without taking them off form service. However, on-site partial discharger detection on XLPE cables and cable accessories are very difficult of variable noise interference, which gives much trouble to partial discharge detecting. This paper introduced in adaptive filter stationary-non stationary filter based oil the wavelet transform (WTST-NST) to denoise the stationary noise interference in partial discharge detecting. The proposed method is a wavelet domain filtering technique, based on the iterative multi-resolution decomposition reconstruction (MRD-MRR) with hard threshold, for extracting PD signals from stationary interference noise. Quantitative and qualitative analysis of the experimental results, while using the WTST-NST filter to PD signals recorded from XLPE and metro DC cables, prove that the ability to extract the PD from noise hidden in it.