NOVELTY - Hydrogen internal combustion engine gas supply device comprises a liquid ammonia storage tank (1), a cooling device (2), a reservoir (3) and an ammonia decomposer (4). The ammonia decomposer comprises a shell (41). The internal part of the shell is a plate body provided with a heat insulation cavity. The internal shell is mutually connected and equipped with first and second ammonia decomposing cavity. The internal part of the first and second ammonia decomposing cavity is uniformly filled with iron catalyst. The left side wall of the shell is provided with an insulation cavity.    USE - Used as hydrogen internal combustion engine gas supply device.    ADVANTAGE - The device: uses internal combustion engine tail gas temperature for decomposition of ammonia in ammonia decomposer, thus increasing economic benefit, and completely reducing of tail gas discharge, to prevent engine pollution.    DETAILED DESCRIPTION - Hydrogen internal combustion engine gas supply device comprises a liquid ammonia storage tank (1), a cooling device (2), a reservoir (3) and an ammonia decomposer (4). The ammonia decomposer comprises a shell (41). The internal part of the shell is a plate body provided with a heat insulation cavity. The internal shell is mutually connected and equipped with first and second ammonia decomposing cavity. The internal part of the first and second ammonia decomposing cavity is uniformly filled with iron catalyst. The left side wall of the shell is provided with an insulation cavity and connected to a first air inlet pipe. The right side upper wall of the shell is provided with first ammonia decomposing cavity and connected to a second air inlet pipe. The bottom end surface of the shell is equipped with second ammonia decomposing cavity and a mixed gas output pipe. One side of the mixed gas output pipe is set with a heat insulation cavity having an exhaust pipe. The mixed gas output pipe is connected to the cooling device through pipeline. The cooling device is connected with reservoir through pipeline. The reservoir is connected to internal combustion engine via pipeline having an air inlet. The discharge port of internal combustion engine is connected with the first air inlet pipe and second air inlet pipe through pipeline connected with a carburetor. The carburetor is connected to liquid nitrogen storage tank through a pipeline.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the (1) Liquid ammonia storage tank #(2) Cooling device #(3) Reservoir #(4) Ammonia decomposer #(41) Shell