The power supply for ocean robots has always been an important issue since it has a fatal influence on the endurance of these vehicles. However, the marine renewable energy (MRE) has huge potential and can provide the possibility to solve this problem between essential endurance and finite energy in ocean robots. This paper starts with brief introduction of marine energy resource and ocean robots and presents significance of improving ocean robots' endurance, through comparison of their performance characteristics. MRE applied in ocean robots developed or under development, including energy conversion and driving principle, is reviewed, such as solar, wind, tides, waves, thermal energy, etc. Many challenges and difficulties are also discussed in energy exploitation and utilization related to ocean robots. Finally, the prospect for the future development of related technologies is proposed in this paper.