Air　quality　is　highly　related　to　the　health　of　a　human　being.　Urban　morphology　has　a　significant　influence　on　air　quality;　however,　the　specific　relationship　between　urban　morphology　characteristics　and　air　quality　at　the　neighborhood　scale　has　yet　to　be　investigated,　especially　the　vegetation　effect　on　PM2.5　concentration　and　diffusion.　The　relevant　morphological　parameters　based　on　the　affected　pathways　of　urban　morphology　on　air　quality　were　selected,　and　the　sensitivity　degree　and　laws　of　the　selected　morphological　parameters　to　PM2.5　were　quantified　by　numerical　simulation,　bivariate　correlation　analysis,　and　regression　analysis.　The　results　showed　that　Building　Density　(BD),　Block　Envelope　Degree　(BED),　Average　Building　Volume　(ABV),　Average　Building　Floors　(ABF),　Standard　Deviation　of　Building　Height　(SDH)　and　Greenbelt　Coverage　Rate　(GCR)　were　Sensitive　Morphological　Parameters　(SMPs).　A　positive　and　cosine　curve　trend　of　BD　and　BED　with　PM2.5　was　observed.　GCR　was　significant　to　dust　retention　along　with　vertical　canopy　height.　When　ABV　=　40,000　m3　and　ABF　=　20F,　the　lowest　PM2.5　concentration　was　examined,　while　increased　SDH　could　promote　airflow　and　enhance　the　capacity　of　PM2.5　diffusion.　Finally,　morphology-optimization　strategies　were　proposed　at　the　neighborhood　scale:　(1)　Decreasing　the　BED　along　the　street;　(2)　considering　the　species　of　vegetation　with　the　appropriate　height　and　increasing　the　GCR;　(3)　increasing　the　ABF　of　neighborhoods　appropriately　while　controlling　the　ABV　and　distinguishing　the　internal　SDH　of　neighborhoods.　The　study　could　apply　the　scientific　basis　for　the　planning　and　design　of　healthy　and　livable　cities.　©　2022　by　the　authors.　Licensee　MDPI,　Basel,　Switzerland.