The present invention discloses an industrial solid waste incinerator and flue gas treatment apparatus, comprising a water-cooled feed hopper, a water-cooled grate and a chamber which are connected in sequence. A front arch, a rear arch and side walls which are formed of membrane water-cooled walls, are provided between the water-cooled grate and the chamber, and a dechlorination tower is arranged behind the chamber. Two sets of rear secondary air pipes, which comprise an upper set of rear secondary air pipes and a lower set of rear secondary air pipes, are arranged on the rear arch, and a dry desulfurization device is arranged between the two sets of rear secondary air pipes, so that the reaction medium and the flue gas are sufficiently disturbed and mixed, and stroke is extended.