In order to solve the problem of positioning irregularity of high-speed railway contact wire in actual operation， a method based on Choi-Williams spectral kurtosis （CW-SK） and quadratic time-frequency analysis is proposed. Since CW-SK is highly sensitive to abrupt transition signals， the irregular components of pantograph-catenary contact pressure can be identified. On this basis， the quadratic time-frequency analysis of the irregular reconstructed signal is carried out to determine the spatial location of different wavelengths on the contact wire. The final test results show that the method can accurately identify and locate the irregularities of contact wire， and there are no other interference components in the time-frequency diagram. Furthermore， the method has good anti-noise performance， which can meet the actual operation requirements of high-speed railway. This paper can provide some references for the evaluation of the contact wire irregularity state and the later maintenance of catenary.