Abstract: The hot compression test of FGH96 superalloy made by hot isostatic pressing was carried out on Gleeble-1500 thermal simulator at 1075℃ with the deformation of 70% under the deformation rate of 0.001 s^-1. Field emission scanning electron microscopy, transmission electron microscopy, and electron spectroscopy were used to study the composition of prior particle boundary (PPB), the role of PPB on the recrystallization FGH96 superalloy was investigated, and the effect of alloy thermal deformation on PPB was analyzed. The results show that, the prior particle boundary in hot isostatic pressed FGH96 superalloy mainly consists of Ti carbide and γ' phase. The PPBs play the promoting role on recrystallization nucleation and hinder the grain growth. The thermal deformation can improve the distribution of PPB, which is in favour of the grain growth process.