The high temperature titanium alloy with rare earth element Nd addition was prepared by rapidly solidified powder metallurgy (RS－PM) processing. The microstructure of RS－PM high temperature titanium alloy has been investigated systemically. Microstructure study showed that the α' martensite phase in the RS powders initially decomposed at 700 ℃ and vastly at 900 ℃during the hot isostatic pressing (HIP) process. The decomposition products were equiaxed or lamellar α phase as well as grain boundary β phase. The microstructure of the specimen HIPed at the temperature in (α+β) phase field contained equiaxed α phase, lamellar α phase and β phase. The size of equiaxed α phase increased while the aspect ratio of the lamellar α phase decreased when the HIP temperature increased. The microstructure of the specimen HIPed at the temperature in β phase field contained coarsed lamellar α phase, grain boundary α phase and β phase. The microstructure became finer with decreasing the powder particle size. The microstructure of the sample HIPed in the (α+β) phase field and then heat treated in the (α+β) phase field was bi－modal microstructure containing equiaxed α phase and β transformed structure. The microstructure of the sample HIPed in the β phase field and then heat treated in the (α+β) phase field was ternary microstructure containing equiaxed α phase, lamellar α phase and β transformed structure. The microstructure of the sample HIPed in the (α+β) phase field or β phase field and then heat treated in the β phase field was basket－weave structure. The proportion of rich－Nd phases increased with increasing the Nd content,resulting in the reduction of original β grain size.