Abstract: In order to carry out high-voltage cable inspection and maintenance economically and efficiently, an optimization method for high-voltage cable inspection cycle based on time delay theory and economic benefit analysis is proposed. Firstly, based on the delay-time concept, the progress of cable failure was regarded as a two-stage process, namely a stochastic process of occurrence and development of defects. Secondly, a mathematical model of the development of cable failures was established according to the service duration of a cable and its historical periodicity of inspection. The time and space characteristics of cable failures were taken into account, and the mathematical model of the expected number of failures of each cable components with the periodicity of inspections was set up, where cable components within different service ages were considered individually. Then, the maintenance activities were optimally scheduled by setting the objective functions as the minimal maintenance cost. Finally, the optimal approach was applied theoretically to thousands of cable circuits of China Southern Power Grid that were put into operation within 10 years. As can be seen from the case study in the paper, the economic expenditure could be reduced by 40% theoretically, compared with the total cost before optimization. It is shown that the total cost of cable failure and daily maintenance can be reduced effectively, and the optimal approach proposed in the paper can be used a guide for actual maintenance and test scheduling.