A nitrous oxide decomposition self-pressurization system comprises a nitrous oxide storage container, a membrane valve, a small-size pressurizer, a flow adjuster, a controller, a decomposer, a check valve, a cooler, a filter and a voltage stabilizer. Based on the the prior art, the invention provides the nitrous oxide decomposition self-pressurization system and the self-pressurization of the system is realized by pressurizing the storage container by using the self-decomposition product of nitrous oxide. By means of the system, a power device that uses the system does not need to carry an extra pressurizing medium and special equipment, so that the structure volume and weight of the power device can be reduced and the requirement for a small-size and light-weight pressurizing system of various power devices such as a solid-liquid mixed rocket engine, a liquid engine and a multi-modal propulsion system that use nitrous oxide as an oxidizing agent can be met.