Based　on　the　one-dimensional　and　unsteady　flow　theory　of　gas　dynamics　and　acoustic　analysis　method,　a　thermodynamics　and　acoustics　model　of　single　cylinder　diesel　engine　was　established,　then　the　model　was　realized　using　GT-Power.　A　method　combined　with　mechanic　analysis　and　acoustic　prediction　was　presented.　With　this　method,　the　influence　of　compression　ratio,　inlet　and　outlet　channels,　intake　valve　and　exhaust　valve　timing　on　engine　exciting　force　and　noise　is　analyzed.　Then　the　optimization　value　of　each　factor　is　determined　to　improve　the　muffler.　The　intake　and　exhaust　noise　of　the　optimized　engine　is　simulated　with　this　model,　the　simulating　results　indicated　that　the　exhaust　noise　reduces　2.6~3dB,　and　the　intake　noise　reduces　1.1~1.4dB.　©　(2013)　Trans　Tech　Publications,　Switzerland.