Pulsating heat pipe (PHP) is an interesting heat transfer device. In this paper we focus 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 the total temperature differences (from the evaporator to condenser) and the evaporator temperature fluctuations are relevant to operating temperature. The minimal total temperature difference and temperature fluctuation appear at an operating temperature ranging from 120°C to 160°C. Experimental analysis of the evaporator temperature fluctuations show that single phase cooling in PHP causes a large total temperature difference and temperature fluctuation. Phase change proportion increases at the optimal operating temperature. Static mechanical balance combining with dynamic elastic oscillation system is used to interpret PHP temperature variations versus the operating temperature.