In　model　2102QB　compression　ignition　engine,　using　HORIBA　MDLT-1302　exhaust　gas　sampling　system　and　electrical　low　pressure　impactor　(ELPI),　the　particulate　matter　(PM)　emission　characteristics,　including　mass　emission　and　PM　number　distribution　were　experimentally　investigated　while　fueled　with　diesel　and　dimethyl　ether　(DME)　fuels　respectively.　Results　show　that,　when　the　engine　running　with　diesel　fuel,　PM　emissions　are　composed　of　agglomeration　mode　particles　with　mean　diameter　of　0.05~0.3　μm;　when　fueled　with　DME,　they　are　mainly　nuclei　mode　particles　with　diameter　under　0.05　μm.　The　number　concentration　of　PM　for　diesel　fuel　is　higher　1~2　magnitude　orders　than　DME.　With　engine　speed　increasing,　the　PM　number　concentration　for　both　two　fuels　increases,　and　the　PM　mass　concentration　also　increases　for　DME　engine,　however,　it　decreases　for　diesel　fuel.　With　engine　load　increasing,　PM　number　and　mass　concentrations　for　diesel　fuel　increases,　especially　in　high　load　area,　however,　DME　fuel　PM　mass　concentration　exhibits　a　growth-decline　trend　with　the　factor　ttq·exp　(n/1000)　increasing,　positions　of　maximum　mass　concentrations　for　all　engine　speeds　are　the　same　basically.　Except　for　full　speed　low　load　conditions,　at　partial　load,　DME　fuel　PM　mass　concentration　is　0.44%~16.6%　of　diesel　fuel,　at　full　load　and　all　speeds　the　fraction　is　in　range　of　0.44%~0.98%.