Non-road　mobile　sources　(NRMS)　are　potential　important　contributors　to　air　pollution　in　China.　However,　their　extreme　impact　on　air　quality　had　been　seldom　studied.　In　this　study,　the　emission　inventory　of　NRMS　in　mainland　China　during　2000–2019　was　established.　Then,　the　validated　WRF-CAMx-PSAT　model　was　applied　to　simulate　the　contribution　to　the　atmospheric　PM2.5,　NO3−,　and　NOx.　Results　showed　that　emissions　increased　rapidly　since　2000　and　reached　a　peak　in　2014–2015,　with　an　annual　average　change　rate　(AACR)　of　8.7–10.0%;　after　then,　the　emissions　were　relatively　stable　(AACR,　−1.4–1.5%).　The　modeling　results　indicated　that　NRMS　has　become　a　crucial　contributor　to　the　air　quality　in　China:　from　2000　to　2019,　the　contribution　to　PM2.5,　NOx,　and　NO3−　significantly　increased　by　131.1%,　43.9%,　and　61.7%;　and　for　NOx,　the　contribution　ratio　in　2019　reached　24.1%.　Further　analysis　showed　that　the　reduction　(−0.8%　and　−0.5%)　of　the　NOx　and　NO3−　contribution　ratios　was　much　lower　than　that　(−4.8%)　of　NOx　emissions　from　2015　to　2019,　implying　that　the　control　of　NRMS　lagged　behind　the　national　overall　pollution　control　level.　The　contribution　ratio　of　agricultural　machinery　(AM)　and　construction　machinery　(CM)　to　PM2.5,　NOx,　NO3−　in　2019　was　2.6%,　11.3%,　8.3%　and　2.5%,　12.6%,　6.8%,　respectively.　Although　the　contribution　was　much　lower,　the　contribution　ratio　of　civil　aircraft　had　the　fastest　growth　(202–447%).　Moreover,　an　interesting　phenomenon　was　that　AM　and　CM　had　opposite　contribution　sensitivity　characteristics　for　air　pollutants:　CM　had　a　higher　Contribution　Sensitivity　Index　(CSI)　for　primary　pollutants　(e.g.,　NOx),　∼1.1　times　that　of　AM;　while　AM　had　a　higher　CSI　for　secondary　pollutants　(e.g.,　NO3−),　∼1.5　times　that　of　CM.　This　work　can　provide　a　deeper　understanding　for　the　environmental　impact　of　NRMS　emissions　and　for　the　control　strategy　formulation　of　NRMS.　©　2023　Elsevier　Ltd