Kaolinite was utilized as in-furnace sorbent to control submicron lead (Pb) and cadmium (Cd) emissions during waste incineration in a fluidized bed furnace. The secondary combustion chamber temperature ranged from 850 to 1000°C. The metal capture was investigated for aspects of chemical reaction, physical conglutination and control performance of submicron metal emission. Pb reacted with kaolinite and caused conglutination of nanoscale metal particles at a lower temperature than Cd. Emission control of submicron Pb was far more effective than that of submicron Cd, particularly below 950°C. For both Pb and Cd, there was capture limitation and an increase of kaolinite fraction above 3% could not further reduce the submicron metal emission. According to toxicity factors (5 Pb = 1 Cd) and the leaching fraction of submicron particles, the comprehensive performance of kaolinite was evaluated and numerous contradictory results were obtained.