A　3D　numerical　model　of　the　municipal　solid　waste　incineration　(MSWI)　process　was　constructed　based　on　a　grate　furnace　with　a　daily　processing　capacity　of　800　tons.　Fluent　was　used　for　analyzing　key　factors　affecting　the　concentration　and　diffusion　level　of　particulate　matter　(PM).　According　to　the　actual　MSWI　plant　working　condition,　a　3D　model　of　the　incinerator　and　the　waste　heat　boiler　has　been　constructed　under　benchmarks.　Key　factors　affecting　PM　generation　were　determined　by　combining　mechanistic　knowledge　and　experts＇　experience.　They　were　the　combustion　temperature　of　solid　phase　municipal　solid　waste　(MSW),　the　wall＇s　PM　collision　mode,　and　the　second　baffle　length.　Subsequently,　the　process　of　resolving　the　3D　numerical　model　was　delineated.　Then,　a　univariate　analysis　of　the　aforementioned　3D　model　was　conducted　for　the　three　pivotal　factors　mentioned　above.　Conclusively,　the　effect　of　the　important　factors　on　the　number　of　particles　at　the　outflow　of　the　incinerator　was　analyzed　via　orthogonal　experiments　to　obtain　the　optimal　combination.　PM　concentration　initially　diminished　and　then　rose　with　the　increased　combustion　temperature　of　the　solid-phase　MSW.　Furthermore,　a　noteworthy　reduction　in　PM　concentration　was　observed　when　the　second　baffle　length　was　12.45-12.95　m.　The　greatest　influence　on　the　PM　concentration　of　the　outlet　was　posed　by　the　wall＇s　PM　collision　mode,　followed　by　the　second　baffle　length.　The　appropriate　adjustment　of　the　combustion　temperature　of　the　solid-phase　MSW,　selection　of　wall　materials,　and　design　of　the　second　baffle　length　were　beneficial　for　diminishing　PM　concentration　and　ensuring　long-term　stable　operation　of　the　MSWI　process.　The　combinative　optimality　of　the　three　key　factors　was　acquired　via　orthogonal　experiments,　which　proved　the　subsequent　optimal　control　of　PM　concentration　at　the　outlet.