Abstract: In recent years, the circuit number and operation life of high voltage (HV) cross-linked polyethylene (XLPE) cable lines continue to increase, which brings a severe challenge to the operation-maintenance personnel in power grid. The existing detection methods and test data cannot provide comprehensive information about the system status, while the survey-based scoring methods have been criticized for theoretical insufficiency and poor quantitative characterization. In this paper, a condition assessment system of HV XLPE cable line is constructed based on the combination of operation-maintenance information and on-line detection data. On the one hand, an operation-maintenance scoring table is designed, which includes four modules of life, load, fault, and environment, to comprehensively reflect the overall status of the cable and accessories. On the other hand, the data of three on-line tests, including the infrared thermal imaging, metal sheath grounding current and partial discharge measurement, are chosen to characterize the real-time system performance. Besides, through the application of typical failure rate curve, correlation analysis, and analytic hierarchy process, the rationality of item design and the effectiveness of weight allocation are improved. The system can work when some inputs are missing, which expands its engineering practicability. Finally, the status of five retired 110 kV cable lines are evaluated by the comprehensive condition assessment system, including comparing the experimental results of the breakdown strength, carbonyl index and crosslinking degree measured on the XLPE insulation samples taken from the cables. The consistency between the test results and the evaluation conclusions can be a good verification for the design of the evaluation system.