Determining　the　status　of　the　municipal　solid　waste　incineration　(MSWI)　process　due　to　the　composition　variations　of　MSW,　operational　differences　of　the　MSWI　plants,　and　maintenance　uncertainties　of　the　incineration　devices　is　difficult.　Moreover,　the　optimal　control　algorithms　developed　off-line　lack　the　support　of　the　incineration　mechanism.　These　conditions　complicate　the　cost-effective　operation　of　the　MSWI　plants.　The　development　of　customized　numerical　simulation　models　can　simulate　the　incineration　effects　and　obtain　the　extreme　value　of　key　process　parameters　to　support　its　operational　optimal　control.　This　article　aims　to　review　the　mechanical　characteristics　and　numerical　simulation　methods　of　the　MSWI　process　based　on　mechanical　grates,　thus　providing　support　for　the　construction　of　a　customized　numerical　simulation　model　and　the　realization　of　a　digital　twin　system　for　the　actual　MSWI　process.　First,　the　mechanical　characteristic　of　the　MSWI　process　is　comprehensively　analyzed.　Then,　the　numerical　simulation　method　based　on　commercial　and　self-developed　software　is　summarized　and　compared.　Furthermore,　the　difficulties　in　creating　customized　numerical　simulations　and　constructing　digital　twin　models　are　discussed.　Finally,　the　conclusion　and　research　directions　are　established　on　the　basis　of　the　concluding　ideas　and　specific　commentaries.　Results　show　that　coupling　several　types　of　software　can　facilitate　the　creation　of　customized　simulations　based　on　actual　process　data.　The　development　of　an　intelligent　digital　twin　encounters　several　difficulties　that　must　be　highlighted　because　the　combination　of　the　numerical　simulation　model　of　the　entire　process　can　analyze　the　mechanism　and　the　realization　of　matching　the　model　with　actual　process　data.　The　current　study　revealed　that　the　digital　twin　model　based　on　mechanical　characteristics　and　numerical　simulations　by　using　actual　process　data　and　artificial　intelligence　technology　could　play　a　significant　role　in　the　safety　and　operation　optimization　of　the　MSWI　process.