Effects　of　diluent　gases　composition　on　ignition　delays　of　dimethyl　ether　(DME)　were　investigated　at　compressed　pressure　of　1.5　MPa,　compressed　temperature　from　670　K　to　795　K　and　equivalence　ratio　of　1　by　using　a　rapid　compression　machine　(RCM).　The　diluent　gases　considered　were　nitrogen　(N2),　mixture　of　N2　and　argon　(Ar)　at　mole　ratio　of　50%　to　50%　and　mixture　of　Ar　and　carbon　dioxide　(CO2)　at　mole　ratio　of　61.2%　to　38.8%.　The　simulation　study　was　performed　over　a　wider　temperature　range　based　on　CHMKIN-PRO　software.　The　results　showed　that　diluent　gases　composition　had　little　impact　on　the　first-stage　ignition　delay.　However,　significant　differences　in　the　total　ignition　delay　were　observed,　especially　in　the　negative　temperature　coefficient　(NTC)　region.　Compared　with　N2,　mixture　of　N2　and　Ar　decreased　the　total　ignition　delay　by　30%.　The　chemical　effect　of　diluent　gases　composition　on　the　first-stage　and　total　ignition　delays　was　negligible.　The　thermal　effect　was　dominant　factor　in　the　low　temperature　and　NTC　regions,　however,　the　chemical　effect　of　CO2　enhanced　and　exceeded　the　thermal　effect　in　the　temperature　region　beyond　the　NTC　region.　With　the　increase　of　N2　dilution　ratio,　the　first-stage　ignition　delay　was　slightly　increased,　while　a　significant　increase　in　the　total　ignition　delay　was　observed.　Moreover,　the　NTC　behavior　of　total　ignition　delay　was　noted　to　become　more　pronounced　at　high　N2　dilution　ratio.　©　2017,　Chinese　Society　of　Agricultural　Machinery.　All　right　reserved.