In this study, pulverized coal bias ignition experiments were conducted in a 250 kW pilot-scale bias combustion simulator to investigate the effects of the combustion conditions on the particulate matter (PM) formation characteristics in a reducing atmosphere; the amount of PM10 was determined using an electrical low-pressure impactor. The particle size distributions of PM10 from pulverized coal bias ignition under various combustion conditions in a reducing atmosphere differ from those in the tail flue gas of a coal-fired boiler. Mainly PM0.38 is produced when the pulverized coal concentration (PCC) is 0.53, the lowest amounts of PM0.38 and PM0.38-10 are produced when the PCC is 0.4, and mainly PM0.38-10 is produced when the PCC is 0.33; the PCC significantly affects formation of PM0.5-0.794. As the bias concentration ratio (BCR) of the pulverized coal increases, the pulverized coal jets are prone to releasing viscous minerals, which easily coalesce into supercoarse particles of size greater than 10 mu m; this decreases the formation of PM0.38 and PM0.38-10. The released viscous minerals are the main sources of PM0.38, and the BCR. significantly affects PM0.205-0.5 formation. Volatiles and char burn most intensely at a primary air velocity (PAV) of 17 m/s, resulting in maximum production of PM0.38 and PM0.38-10. PM0.38 was mainly produced in the volatile combustion stage, and PM0.38-10 was mainly produced in the char combustion stage; the PAV significantly affects the formation of PM0.041-0.317. More PM10 with a larger fraction of ultrafine PM was produced at the optimum PAV, which was selected based on the ignition characteristics.