Abstract: Insulation condition of cables is closely related to the safe operation of metro, thus conducting a status assessment of cables in urban rail transit is of great significance.Operation status of cables in Shanghai Metro was introduced, failure mechanisms of cables was studied, and stresses that cables might experience during operation was analyzed, such as environmental conditions stress and mechanical stress. Based on the analysis, cables that should be evaluated were selected, evaluation rules for the cables were formulated, and clear testing methods were established to provide recommendations for the inspection and maintenance of cables.