In　order　to　study　the　essential　structural　characteristics　of　monolayer　MoS2　nanoribbons　in　natural　state,　and　also　the　effects　of　the　aspect　ratio　and　the　ambient　temperature　on　the　relaxation　properties　of　the　nanoribbons,　the　relaxation　properties　of　monolayer　MoS2　nanoribbons　with　different　aspect　ratios　are　simulated　by　molecular　dynamics　(MD)　method　based　on　REBO　potential　functions　at　different　thermodynamic　temperatures　from　0.01　K　to　1500　K.　The　energy　curves　and　surface　morphologies　of　monolayer　MoS2　nanoribbon　are　obtained,　and　the　dynamic　equilibrium　process　of　the　monolayer　MoS2　nanoribbons　is　also　discussed　in　all　the　simulation　process.　The　simulation　results　show　that　the　monolayer　MoS2　nanoribbons　do　not　generate　a　fluctuation　at　the　ideal　temperature　(0.01　K)　for　the　reason　that　the　kinetic　energy　of　the　monolayer　MoS2　nanoribbons　is　almost　zero　and　the　vibration　amplitude　is　small.　However,　a　certain　degree　of　fluctuations　occurs　at　the　edges　and　inside　of　the　monolayer　MoS2　nanoribbons　at　the　room　temperature　or　high　temperature.　The　fluctuation　height　and　the　fluctuation　degree　also　increase　with　increasing　the　ambient　temperature　and　the　aspect　ratio　of　the　MoS2　nanoribbon,　even　a　high　aspect　ratio　monolayer　MoS2　nanoribbon　exhibits　a　surface　curved　fluctuation,　which　is　perpendicular　to　the　surface　of　the　MoS2　nanoribbons　under　high　temperature　condition.　Finally,　the　influences　of　chirality　on　relaxation　property　under　different　temperature　conditions　are　studied　in　this　paper　further,　the　results　show　that　unlike　the　armchair　structure,　the　zigzag　monolayer　MoS2　nanoribbons　not　only　present　a　surface　fluctuation,　but　also　exhibit　an　obvious　bending　phenomenon　along　the　width　direction　simultaneously.　Like　the　armchair　nanoribbons,　the　surface　fluctuation　height　and　the　surface　fluctuation　degree　of　the　zigzag　nanoribbons　also　increase　with　increasing　both　the　ambient　temperature　and　the　aspect　ratio　of　the　MoS2　nanoribbons.　It　is　also　observed　that　the　armchair　and　zigzag　monolayer　MoS2　nanoribbons　with　a　similar　aspect　ratio　have　a　similar　surface　fluctuation　degree　at　the　same　ambient　temperature.　Unlike　the　armchair　nanoribbons,　the　bending　phenomenon　along　the　width　direction　of　the　zigzag　nanoribbons　is　more　significant,　and　the　bending　width　and　the　bending　degree　increase　with　increasing　the　ambient　temperature　and　the　aspect　ratio　of　the　MoS2　nanoribbons.　Although　the　bending　degree　of　the　zigzag　nanoribbons　becomes　larger　with　the　increase　of　temperature,　the　increasing　rate　of　the　bending　degree　will　become　smaller　and　smaller　until　the　bending　degree　reaches　a　maximum　value.　©　2016　Chinese　Physical　Society.