Abstract: The concept of relay heat pipe system was put forward aiming at the problem of extremely low reliability because of the special structure of single over long gravity heat pipe, which was used to exploit the heavy oil. The heat transfer performance of the relay heat pipe system was investigated simulating the actual environmental conditions of heavier oil exploitation to confirm the relay heat transfer performance. The results show that the relay gravity heat pipe system could transfer the heat， and its total heat transfer performance was weaker than that of the single over long heat pipe，but could remedy the defect of extremely low reliability of single over long heat pipe.