Book excerpt: This thesis focuses on ULF (Ultra-low-frequency) waves' interaction with plasmasphere particles and ring current ions in the inner magnetosphere. It first reports and reveals mutual effect between ULF waves and plasmasphere using Van Allen Probes data. The differences and similarities of different ring current ions interacting with ULF waves are extensively explored using Cluster data, which provides a potential explanation for O+-dominated ring current during the magnetic storms. Furthermore, this thesis finds a method to study the phase relationship between ULF waves and drift-bounce resonant particles, and proposes that the phase relationship can be used to diagnose the parallel structure of standing wave electric field and energy transfer directions between waves and particles. The findings in this thesis can significantly promote our understanding of ULF waves' role in the dynamics of inner magnetosphere.