Abstract: A distributed parameter model is postulated to describe in detail the heat transfer and flowing process in the evaporator of Capalary Pumped Loop(CPL)system.Compared with the previously developed lumped parameter model,the present one gives the detailed temperature distribution of solid wall and vapor,the heat convection coefficient,the heat exchange coefficient in phase change and the thermal states of vapor along the axial distance of CPL evaporator,thus establishes a reasonable foundation for revealing in detail the heat transfer performance of CPL evaporator and further experimental study on its engineering model as well as for optimization.