Following the characterization of thiohemiaminal type nuphar alkaloids with immunosuppressive activity, four new thiaspirane sulfoxide type dimeric sesquiterpene alkaloids, nupharpumilamines A, B, C, and D, were isolated from Chinese Nupharis Rhizoma, the dried rhizoma of Nuphar pumilum (TIMM.) DC. The structures of nupharpumilamines A, B, C, and D were determined on the basis of chemical and physicochemical evidence.