Experimental investigation was conducted on closed-loop pulsating heat pipe（CLPHP）working with a mixture of water and mercury.The temperature fluctuation of the evaporator section at different inclination angles was measured at constant heating load，and the phenomenon of start-oscillation in micro inclination angles was observed.Then the operation characteristics of Hg-H2O PHP and pure H2O PHP was compared in the same fill ratio.Lastly，a comparison of heat transfer performance of Hg-H2O PHP with different inclination angles was made.The results showed that the addition of mercury into water effectively assisted the start-oscillation in micro inclination angles which increased the application flexibility of the PHP system.Thermal resistance decreased as heating load increased.Up to a certain magnitude，different inclination angles had very close thermal resistance.It was discovered that the critical heat flux of start-oscillation was related to heating history.