We developed an oxidant- and transition-metal-free approach to construct six-membered cyclic phosphinamides via an intramolecular electrochemical C-H phosphinamidation process. With nBu4NBr as the catalyst and electrolyte, cyclic phosphinamides bearing a variety of functional groups (22 examples) were readily accessed under mild conditions. Meanwhile, this protocol provided an alternative route to organic electroluminescent materials and P-N ligands.