Abstract: Fly ash was sampled at the inlet and outlet of low-low temperature electrostatic precipitator（LLT-ESP） on a 1000 MW coal-fired unit. The composition of fly ash collected by specific field of LLT-ESP was measured by X-ray fluorescence. The mass of particulate matter, elemental size distribution of fly ash and particulate matter（PM） removal efficiency of LLT-ESP were studied. The results show that the PM removal of LLT-ESP can be enhanced by reducing inlet flue gas temperature to Low-Low temperature（87~100℃）, the efficiency may reach above 99.9%, escaping fly ash concentration can be controlled within 20mg/m3; PM₁ removal rate could be up to 99.44% via adjusting the inlet flue gas temperature to 90℃. Elements of Si and Al mainly distributed in coarse particles（particle size above 10μm）, while elements of Ca, Fe, Mg, S mainly enriched on inhalable particulate matter（PM10） collected by LLT-ESP.