The invention provides a hypersonic speed aircraft cooling system based on ammonia water Rankine cycle, which relates to a hypersonic speed aircraft cooling system. The hypersonic speed aircraft cooling system aims to solve the problems that the prior hypersonic speed aircraft, in particular to a scramjet is difficult to cool, and has large flow of a cooling fuel and insufficient heat sink. One end of a center shaft is connected with a generator, and the other end of the center shaft is connected with a circulating pump and a fuel pump respectively, a steam turbine is arranged on the center shaft and between the circulating pump and the generator, and a cooling channel is arranged on the outer wall surface of the upper part of an engine. The hypersonic speed aircraft cooling system is applied to the thermal protection of the hypersonic speed aircraft and the cooling of the scramjet.