Abstract: Leaching process of typical heavy metal Zn in MSWI (municipal solid waste incineration) fly ash when pH was controlled about 4 had been studied with the tests of EDS, XRF and SEM. Kinetic model for this leaching process was established through constant temperature method. The results showed that sphere controlled by internal diffusion model was appropriate for the leaching process of Zn. SEM tests revealed that most of MSWI fly ash particles maintained spherical or similar microstructure during the reaction though the surface of MSWI fly ash particles had dissolution at different level, which offered microscopic scales of evidence for sphere controlled by internal diffusion model. The relation between Zn leaching rate and reaction time (t) can be represent as 1-3(1-X)^2/3+ 2X = 18.25exp(-2 385.25T)/t with approximately 19. 831 kJ/mol apparent activation energy under experimental conditions.