This paper describes the current status of the design study and the related research and development for an advanced loop-type fast reactor: the Japan sodium-cooled fast reactor (JSFR). First, the development targets and the major design requirements are established. Then, a cost-down approach in which developing innovative technologies is key to being competitive with another future energy source is discussed. Here, the development status of several innovative technologies such as a two-loop cooling system, reliable reactor system, simplified fuel-handling system, passive reactor shutdown system, mitigation measure against a core disruptive accident, and minor actinide-bearing oxide fuel core is described. Last, a review of JSFR development and the demonstration plan for the innovative technologies are discussed.