A　protocol　named　Dynamic　Range-Based　Mobile　Multicast　(DRBMoM)　is　proposed,　which　designs　an　algorithm　based　on　Range-Based　Mobile　Multicast　(RBMoM)　to　dynamically　determine　an　optimal　service　range　for　each　Mobile　Host　according　to　its　mobility　characteristics,　service　traffic　and　some　network　parameters.　DRBMoM　trades　off　between　the　shorter　multicast　delivery　path　and　the　fewer　multicast　tree　reconstruction　frequency　by　designing　a　cost　function　and　searching　the　service　range　minimizing　the　cost　function.　Analyses　are　carried　out　to　show　that　the　cost　function　value　increases　with　the　increase　of　user＇s　service　traffic　and　mobility　rate;　While　the　optimal　service　range　decreases　with　the　increase　of　user＇s　service　traffic　and　increases　with　the　increase　of　user＇s　mobility　rate.　In　addition,　the　cost　function　value　of　DRBMoM　is　smaller　than　that　of　RBMoM,　which　means　DRBMoM　outperforms　RBMoM.　At　last,　analyses　show　that　the　average　handoff　signaling　cost　of　DRBMoM　is　appreciably　higher　than　that　of　the　congeneric　scheme,　while　the　average　multicast　packet　transmission　cost　and　the　cost　function　value　of　DRBMoM　are　all　lower　than　those　of　the　congeneric　scheme.