The　high　energy　noise-like　pulses　(NLPs)　were　experimentally　investigated　in　a　passively　mode-locked　erbium-doped　fiber　laser　with　a　long　ring　cavity　by　using　nonlinear　polarization　rotation　technique.　Large　net　normal　group-velocity　dispersion　of　the　cavity　is　estimated　as　high　as　6.46　ps(2),　which　is　beneficial　to　formation　of　high-energy　pulses.　With　the　total　pump　power　of　970　mW　(the　pump　powers　of　forward　pump　and　backward　pump　are　set　at　the　value　of　455　mW　and　515　mW,　respectively),　a　stable　ultrahigh　energy　rectangular-shape　pulse　emission　with　the　pulse　duration　of　35　ns　was　observed.　The　energy　of　square　packet　with　a　fundamental　repetition　rate　of　141.6　kHz　is　as　high　as　840　nJ.　The　signal-to-noise　is　higher　than　60　dB　in　RF　spectrum.　The　feature　of　NLPs　is　confirmed　by　the　coherent　spike　of　autocorrelation　trace.　When　the　pump　power　is　beyond　970　mW,　the　mode　locking　operation　with　fundamental　repetition　rate　cannot　be　achieved　despite　of　the　large　range　variation　of　polarization　controller　(PC)　settings.　However,　the　forthorder　harmonic　mode　locking　can　be　observed,　the　square　pulse　packet　duration　still　remains　at　similar　to　35　ns.　The　experimental　results　demonstrated　that　the　ultrahigh　energy　NLPs　is　only　realized　at　the　condition　of　special　physical　parameters　and　it　is　restricted　by　the　number　and　intensity　of　ultra　short　pulses　within　the　envelope　to　some　extent.