The invention discloses an instant hydrogen-production power generation system and method. The system comprises a hydrogen-production subsystem, a power generation subsystem and a collection and utilization subsystem, wherein the hydrogen-production subsystem, power generation subsystem and collection and utilization subsystem are connected sequentially; the hydrogen-production subsystem uses methanol water to produce hydrogen, and transfers the produced hydrogen to the power generation subsystem in time through a transfer pipeline for power generation; and the collection and utilization subsystem is connected with an exhaust channel outlet of the power generation subsystem, and is used for collecting water from discharged gas or collecting water as the raw material of the hydrogen-production subsystem. The system and method can collect residual gas discharged from the power generation subsystem, and extract hydrogen, oxygen and water from the residual gas; and the hydrogen and oxygen can be combusted to release heat so as to provide heat energy for the power generation subsystem, and the water can be transferred to the hydrogen-production subsystem for cyclic utilization, so that the system does not need any additional water source. The system and method can enhance the power generation efficiency of the system and save the energy source.