The　recently　discovered　Zhundong　coal　field　is　one　of　the　main　energy　bases　in　China　for　the　huge　prototyped　coal　reserve.　However,　the　Zhundong　coal　causes　seriously　fouling　and　slagging　problems　during　combustion　for　the　high　content　of　Na　and　Ca.　In　this　study,　the　Zhundong　coal　combustion　experiments　were　carried　out　in　drop　tube　furnace　and　the　ashes　sampled　at　different　temperature　were　analyzed　by　SEM-EDS　(scanning　electron　microscope-energy　dispersive　spectrometer)　to　obtain　the　microstructure　and　composition　of　ashes.　The　results　show　that　a　lot　of　Na-based　compounds　and　a　part　of　CaO　could　be　vaporized　during　the　early　stage　of　Zhundong　coal　combustion.　With　the　fume　temperature　decreasing,　the　gaseous　Na　and　Ca　compounds　react　with　SO2　to　form　Na2SO4　and　CaSO4　which　are　divided　into　three　parts.　A　part　condensates　on　the　ash　particle　surface,　and　the　remainder　forms　to　aerosol.　A　fraction　of　aerosol　united　to　form　flocculent　particles　and　adhered　ash　particles　and　the　others　released　to　air　as　fine　particles.