A new design of Langmuir Probe (LP) used for diagnosing plasma in Tokamak has been reported in this work. The thermal state of LP is given by finite element analysis and an explanation of temperature variation based on the changes in heat flux are presented. The evaluation of thermal contact resistance at the interface of different materials are presented. A effective analytical method based on numerical calculation and experimental investigation has been developed for studying the heat transfer capability of LP. This method, is able to predict the inner thermal state of LP, thereby leading to optimize the design of LP. Excellent agreement between simulated results and calculated results figured out by ANSYS and experimental data, indicated the validity of this model. These results obtained are useful for developing the high-performance LP.