Safe disposal of high level radioactive waste is a challenging task facing the scientific and technological world. This paper introduces the latest progress of high level radioactive waste disposal programs in the world,and discusses the key scientific challenges: the precise prediction of the evolution of a repository site; the characteristics of deep geological environment;the behaviour of deep rock mass,groundwater and engineering material under coupled conditions(intermediate to high temperature, geostress, hydraulic, chemical, biological and radiation process, etc); the geochemical behaviour of transuranic radionuclides with low concentration and its movement with groundwater;and the safety assessment of disposal system. Several large-scale research projects and several hot topics relating to high-level waste disposal are also introduced.