Electrical spin,which is the key element of spintronics,has been regarded as a powerful substitute for the electrical charge in the next generation of information technology,in which spin plays the role of the carrier of information and/or energy in a similar way to the electrical charge in electronics.Spin-transport phenomena in different materials are central topics of spintronics.Unlike electrical charge,spin transport does not depend on electron motion,particularly spin can be transported in insulators without accompanying Joule heating.Therefore,insulators are considered to be ideal materials for spin conductors,in which magnetic insulators are the most compelling systems.Recently,we experimentally studied and theoretically discussed spin transport in various antiferromagnetic systems and identified spin susceptibility and the Néel vector as the most important factors for spin transport in antiferromagnetic systems.Herein,we summarize our experimental results,physical nature,and puzzles unknown.Further challenges and potential applications are also discussed.