Pulsating heat pipe (PHP) is an interesting heat transfer device. This paper focuses on PHP heat transfer characteristics versus its operating temperature. In experiments of copper and stainless steel PHPs, results indicate that, at a same input power, both temperature differences (from the evaporator to condenser) and evaporator temperature fluctuations are relevant to operating temperature. The minimal temperature difference and fluctuation appear at an operating temperature ranging from 120 to 160°C. Experimental analysis of the evaporator temperature fluctuations show that single phase cooling in PHP causes a large temperature difference (between the evaporator and condenser) and fluctuation. Phase change proportion increases at the optimal operation condition. Static mechanical balance combining with dynamic elastic oscillation system is used to interpret PHP temperature variations versus operating temperature.