Contact wire wear (CWW) is an important and comprehensive indictor to represent the catenary servicing performance. Due to large spatial range, high accuracy and high efficiency requirements of CWW measurement, a visual method with active structured-light is proposed for the application of CWW onboard monitoring based on the triangulation and Scheimpflug principles. To solve the vision modeling and calibration problems, the Gaussian-Newton nonlinear least square method is investigated. The parameters of homograph matric between image plane and structured-light plane, the coefficients of lens distortions are extracted simultaneously by the crossinteractive numerical optimization approach. The camera calibration for the CWW measurement is established with large field of view and high accuracy, and the corresponding onboard monitoring equipment is developed to meet the field demand. The experimental studies of static calibration and field dynamic test are both carried out. It′s found that the calibration re-projection root-mean-square (RMS) errors of the proposed imaging model is 0. 083 mm, which improves the accuracy of 53. 1% compared to the traditional imaging model. Meanwhile by the comparing the onboard test and manual results, the RMS errors of CWW width, depth and area are within 0. 119 mm, 0. 115 mm and 0. 788 mm 2 , respectively.