A　novel　random　access　(RA)　preamble　format　is　proposed　in　this　paper　to　support　fifth　generation　new　ratio　(5G　NR)　enabled　satellite　system,　which　is　a　low　earth　orbiting　(LEO)　based　non-terrestrial　network　(NTN).　Considering　a　fact　that　traditional　design　of　RA　preamble　can　not　meet　the　link　budget　due　to　a　long　distance　between　the　satellite　and　terminal　on　the　earth,　and　also　will　cause　a　wrong　or　failure　detection　of　PRACH,　or　wrong　timing　estimation　for　uplink　synchronization.　The　frequency　offset　under　the　large　relative　moving　speed　between　the　satellite　and　the　terminal　will　also　increase　the　failure　detection　of　PRACH　(physical　random　access　channel).　Therefore,　a　novel　RA　preamble　format,　i.e.,　a　Zadoff-Chu　(ZC)　sequence　with　multiple　lengths,　are　designed.　To　reduce　the　ambiguous　estimation　of　RA　preamble,　a　symmetric　transmission　of　the　proposed　preamble　is　analyzed.　Further,　two　detection　algorithms　(Algorithm　1　and　Algorithm　2)　are　proposed　to　detect　PRACH.　Simulation　results　validate　that　the　proposed　RA　preamble　can　meet　the　LEO　based　NTN　performance　requirements.　According　to　simulation　results,　it　can　be　proved　that　Algorithm　2　is　more　robust,　considering　timing　error　and　frequency　offset.　©　2022　IEEE.