Abstract: A field measurement study was conducted on typical grate furnaces (GF) and circulating fluidized bed (CFB) waste incinerators. Flue gas and by-products (bottom ash and fly ash) were collected upstream and downstream of different air pollution control devices (APCDs) to investigate the migration and transformation characteristics of mercury (Hg) in the tail-end flue gas. The results showed that mercury in the flue gas existed in multiple forms, predominantly as oxidized mercury (Hg²⁺), followed by particulate-bound mercury (Hg^p), with zero-valent mercury (Hg⁰) accounting for a relatively small proportion. The total mercury (Hg^T) concentration in the flue gas exhibited significant temporal fluctuations, with notable variations in mercury species concentrations across different incineration plants. Different APCDs exhibited varying efficiencies in transforming and removing mercury species. The semi-dry flue-gas desulfurization (SD-FGD) tower promoted the conversion of Hg²⁺ to Hg^p, whereas the fabric filter (FF) demonstrated high removal efficiency (54.35%~95.60%) for various forms of mercury. After incineration, only a small fraction of Hg^T from the waste accumulated in the bottom ash, whereas the majority (78.27%-93.39%) was distributed in the fly ash. Compared with the GF incinerator, the CFB incinerator released a higher proportion of Hg^T during combustion. The mercury emitted into the atmosphere was dominated by Hg²⁺, with an Hg^T emission factor ranging from 0.008 to 0.526 mg/kg.