Ash deposition and fusion during the incineration of high-concentration organic wastewater rich in salt is complicated by various issues, resulting in severe operational problems, such as fouling, slagging, and even unscheduled shutdown. The fusion characteristics and melting kinetics of ash samples collected from an industrial-scale wastewater incineration plant were determined by ash fusion temperature tests, simultaneous thermal analysis, and X-ray powder diffractometry. The results showed that the ash fusion characteristics depended upon not only ash compositions but also mineralogy transformation and evolution. The major melting process of ash sample 1 was within the range of 1158-1196 K. Because of the existence of the low-temperature eutectic compounds Na3Fe(SO4)(3) and Na2Ni(SO4)(2)(.)4H(2)O, the temperature ranges of melting processes of ash samples 2-4 were 200-300 K lower than that of ash sample 1. Weight loss processes in ash sample 5 continued over the whole furnace temperature range. The Coats-Redfern equation was used to approximately evaluate the ash melting kinetics. Ash sample 1 had the highest activation energy for an ash melting process (3125.31 kJ mol(-1)). Ash samples 2 and 5 had relatively moderate activation energies (729.15-1338.93 kJ mol(-1)). Ash samples 3 and 4 had the lowest activation energies (374.00 and 375.68 kJ mol(-1)), which indicated that Na2SO4 melting required more energy than the melting of low-temperature eutectic compounds. The most probable reaction model for all of the melting processes was f(alpha) = (1 - alpha)(2). The most probable reaction model for the melting process at 1163.0-1284.9 K in ash sample 3 was f(alpha) = (1- alpha)(4).