MSW incineration fly ash should be treated safely because it is one of acknowledged hazard solid wastes. Metallurgical sinter has a similar high temperature environment as melting treatment，therefore，it is proposed as hazard-free treatment for MSWI fly ash. Experiments are carried out to investigate the pelleting properties of fly ash and the seperation and solidification of heavy matals in MSWI fly ash iron-bath melting process. The results show that adding 8% cement and 1% agent for solidification，the compressive strength of fly ash pellets is 600~700 N/bellet when its curing period is about 8 ~11 d，achieving the demands for transporting and sintering. By iron-bath melting，more than 90% Mn and Fe in MSWI fly ash are removed and solidified in iron phase，and the distribution ratio of Cr and Cu in iron phase is beyond 70%. The leaching toxicity of molten slag are tested，and the leaching toxicity of all the metals can reach the standard. All the results indicate that the hazard-free treatment for MSWI fly ash by metallurgical sintering is feasible.