By adopting twosection ERT system, the Gasliquid two phase velocity measurement is tramsformed into time delay estimation, due to the ERT has the advantages of high realtime and nonintrusive measuring. The Gasliquid twophase flow signals are mostly nonstationary, hence, cross correlation analysis with traditional time delay algorithms will bring multimodal function which leeds to a serious deviation of twophase velocity measurement. Aiming to improve measuring accurancy and stability, a novel time delay estimationalgorithm is proposed with the lifting wavelet. Based on reweighting method with mother wavelets, the improved threshold lifting wavelet function removes the noise of the raw signal, and the Morphological Lifting Wavelet is utilized to denoise the lagging correlation between the upstream and downstream for time delay estimation to obtain the accurate velocity result.