A large-scale water-fire tube hot water boiler of double-barrel transverse vertical type threaded flue relates to a water-fire tube hot water boiler. The aim of the invention is to settle the problemsof ash accumulation, hard ash elimination, and reduced thermal efficiency of boiler in the prior water-fire tube hot water boiler. A burnout chamber, a convection calandria and a vertical threaded flue coal economizer are provided in the boiler body. The convection calandria is communicated with the upper barrel and the lower barrel. A warm water area and a hot warm water area are installed in the upper barrel. A first connecting pipe is communicated with a lower box of water cooled wall of back wall and the lower drum. A second connecting pipe is communicated with a lower drum and a verticalthreaded flue coal economizer. A third connecting pipe is communicated with a hot water area and the vertical threaded flue coal economizer. The down pipe of water cooled wall of front wall is communicated with a lower collection box of water cooled wall of front wall and the cold water area. The down pipe of left wall is communicated with a lower collection box of water cooled wall of left wall.The down pipe of right wall is communicated with a lower collection box of water cooled box of water cooled wall of right wall. The large-scale water-fire tube hot water boiler of double-barrel transverse vertical type threaded flue according to the invention adopts the vertical threaded flue coal economizer and has the advantages of no ash accumulation in the threaded flue, easy ash eliminationand high thermal efficiency of boiler.