Abstract: The blade tip clearance variation of the high pressure turbine（HPT） has significant effect on the power,the efficiency and the service cycle of gas turbine.The finite element models of the blade,the disk and the shroud were built.The radial displacements were calculated by the thermal structural coupling method.The regulation of the blade tip clearance variation at the practical working states of the turbine was also analyzed.The results show that the temperature dominates the displacements of blade and disk.And the centrifugal force has an extending effect on the rotor than that of the blade.The radial displacements of them are not matching,thus lead to clearance changes.The thermal and the centrifugal force are the two major factors for the variation of tip clearance which was induced by the disharmony of radial displacements.Rapid accelerating and decelerating has the most significant effect on the clearance.