To investigate the effect of condenser location and gravity on operating performance,a miniature loop heat pipe with series flat evaporator were tested.The results show that the loop heat pipe can start up successfully at various positions under a low heat load(20 W) and have good operating performance with Qmax=130 W and R=0.21 /W.At horizontal ℃ al position,the loop heat pipe with shorter vapor line has better start-up performance and higher Qmax.Under a higher heat load,the effect of condenser location on operating performance becomes more noticeable.It is found that a loop heat pipe with series flat evaporator has good anti-gravity capability and can operate with all elevations and tilts.When the loop heat pipe is at vertical position with compensation chamber above the evaporator,its operating performance is the best under the gravity field.