In this talk, I will talk about the search of W' pair in the Littlest Higgs Model with T-parity (LHT) at the LHC. With the W-jet tagging technique, we demonstrate that the bulk of the model parameter space can be probed at the level of more than 5σ in the signal events of two fat W -jets plus large missing energy. Furthermore, we propose a novel strategy of measuring the principle parameter f that is crucial to testify the LHT model and to fix mass spectrum, including dark matter particle. Our proposal can be easily incorporated into the current experimental program of diboson searches at the LHC Run-II.