Abstract: With more and more strict national requirements on the emission of fixed-source particulate matter,it is necessary to conduct in-depth study on the physical and chemical changes of the emission process of particulate matter in the pollutant control system. In this paper,a pollution control system of pulverized coal industrial boiler was designed based on semi-dry desulphurization technology,four measuring points were set along the system,and the particles were sampled at constant velocity,and the particulate matter was tested and analyzed by weighing,laser particle size meter,SEM-EDS and XRD. The results show that the particulate matter concentrations at the four sites are 9.90 g/Nm~3,793.50 g/Nm~3,92.14 g/Nm~3 and 26.72 mg/Nm~3,respectively.The measured concentration of particulate matter at the outlet of flue gas emission is 16.84 mg/m~3,the measured oxygen content is 8.07%,and the emission concentration of particulate matter at the outlet of bag dust collector is 12.69 mg/m~3 when the oxygen content is 9%,which can meet the emission requirements of industrial boiler. Particulate matter at the inlet of the semi-dry desulfurization reactor is mainly composed of boiler outlet fly ash and humidifying circulating ash. The particle size distribution shows a typical bimodal distribution pattern,with the peak value at 0.7 μm and 22 μm.The fraction of particle size less than 1,1.0-2.5,2.5-10 μm and more than 10 μm is 2.38%,2.59%,16.47% and 78.54% respectively;the particle size distribution peak value migrates to the large particle size direction after desulphurization reactor,which appears at 1 μm and 90 μm respectively,and the fraction of particle size varies little. After cyclone separator,the particle size distribution peak value of fly ash particles migrates to small particle size direction,which appears at 0.7 μm and 6 μm respectively. The total concentration and classification concentration of fly ash particles decrease,and the proportion of large particles decreases significantly. The particles of the four measuring points are different in morphology and composition,the irregular structure of the fly ash particles at the outlet of the boiler is more,and there is obvious agglomeration phenomenon,the particle size is larger,and its composition is similar to that of the coal-fired fly ash. At the outlet of desulphurization reactor,the larger irregular porous block structure of fly ash particles decreases obviously,while the content of inhomogeneous regular spherical structure increase,the surface of particles is accompanied by fine irregular substances,and the content of Si,S and Ca elements in element content increase. Through XRD detection and analysis,it is found that the main components of particulate matter before desulphurization are ettringite,SiO_2 and Ca(OH)_2,which are consistent with the components of coal-fired fly ash,and the main components after desulphurization are CaO,CaSO_4·2H_2O and SiO_2,respectively.