Abstract: In recent years， pulsating heat pipe has been widely studied as a kind of element with high heat transfer efficiency， and its application field is very extensive. In order to study the influence of various factors on the heat transfer performance of pulsating heat pipe in low temperature region， a three-dimensional numerical solution model of the closedloop pulsating heat pipe with 6 turns is established by using the multiphase flow VOF method. The results show that when pulsating heat pipe worked stably， the tubes formed a staggered distribution between the riser and the descending tube， in the riser tubes the majority of flow patterns were plug flow and in the drop tube the majority of flow patterns were bubble flow. When heating power was lower， the thermal resistance of pulsating heat pipe decreased as the filling rate increased. For different filling ratio， the thermal resistance increased with the heating power and then increased， the increase of the filling ratio can reduce the influence of the inclination angle on the heat transfer resistance to a certain extent.