A new task-flow based task system has been developed for live-line maintenance tasks done by a live working robot. Its aim is to improve the procession efficiency and intelligent of human-computer interaction. This system design is based on a new approach of task-flow. This paper introduces characteristics and function of each parts of live working task system, impresses connection and relationship between the task flows. The results of a system experiment confirmed that the system enables the live-line maintenance tasks to be performed orderly and efficiently in accordance with the task procedure.