As　the　first　type　of　practical　fountain　codes,　LT　codes　are　used　in　various　applications.　Although　the　performance　of　an　LT　code　is　determined　by　the　parameters　of　the　Robust　Soliton　Distribution　(RSD),　this　relationship　remains　largely　unclear.　In　this　paper,　we　analytically　study　the　relationship　between　the　mean　degree　value　of　the　RSD　and　the　parameters　including　the　spike　position　and　δ　in　RSD.　Then,　with　obtained　properties　and　simulation　results,　we　further　investigate　the　impact　of　these　parameters　on　the　performance　of　LT　codes.　Copyright　©　2014　Inderscience　Enterprises　Ltd.