A restraint fluid inertia storage power assisting device with double-speed superposition action comprises a base, a housing, a main shaft, a main inertia wheel, transmission gears, auxiliary shafts, an auxiliary inertia wheel, a driving gear, a restricted baffle, a flowing solid object, a front end face cover and a rear end face cover , and bearings. The upper part of the base is connected with the bottom part of the housing, the central holes of the front and the rear end faces are respectively with the bearing, the transmission gears with bearings inside the central holes are respectively fixed to the inner sides of the front and the rear end face covers, the middle part of the main shaft is connected with the central hole of the main inertia wheel, a plurality of auxiliary shafts are fixed to longitudinal holes formed on the end face of the main inertia wheel at uniform angles by the bearings, lubricating oil is sealed inside an adding layer, the two sides of auxiliary shafts are connected with the auxiliary inertia wheel and the central holes of the driving gear, the restricted baffle is fixed inside the adding layer of the auxiliary inertia wheel to seal lubricating oil, the outer diameter of the two sides of the main shaft are respectively connected with the inner diameter of the bearing of the transmission gear and the inner diameter of the bearing of the front and the rear end face covers, the driving gear engages with the transmission gear, and the front and the rear end face covers are fixed on the two ends of the housing through screws.