Loop heat pipe (LHP) is a kind of high efficient heat transfer device driven by the capillary force，and flat loop heat pipe (FLHP) is LHP with flat evaporator，which can reduce the thermal resistance between the flat heat source and the evaporator.To make the loop heat pipe a better performance，an FLHP with bi-transport loops (BTL) is designed to reduce the pressure drop and enlarge the condenser cooling area.The evaporator and pipe is made from copper and ultrapure water is filled as the working fluid.Two valves are fixed in the two liquid lines.Experimental results show that，the FLHP can be changed successfully to be an FLHP with BTL or an FLHP with single-transport loop (STL) by controlling the valves，and no big temperature oscillation is observed in the experimental range.The FLHP with BTL has a better performance than that with STL.The evaporator temperature of FLHP with BTL can be 10℃ lower than that of FLHP with STL at 30W.Compared to that of the FLHP with STL，the total thermal resistance of the FLHP with BTL can have a decline rate more than 20% at different power.The reason why the decline rate is much less than 50% is discussed.Compared with the FLHP with STL，the FLHP with BTL can only reduce the thermal resistance caused by the pressure drop in the loop and in the condenser，but it cannot reduce the thermal resistance in the evaporator.If the evaporator is optimized，the decline rate of the total thermal resistance from FLHP with STL to FLHP with BTL would be even larger.