The invention relates to an inertia energy storage system comprising a housing, a stator yoke, stator cores, a stator winding, a stator exciting winding, a magnetic resistance rotor, and a shaft. The stator yoke is fixedly connected with the inner wall of the housing. The shaft is supported in the housing in a rotatable manner through a upper bearing and a lower bearing. The magnetic resistance rotor fixedly sleeves the shaft and comprises a magnetic resistance rotor first segment, a magnetic resistance rotor second segment, and a magnetic resistance rotor connection segment. The magnetic resistance rotor first segment and the magnetic resistance rotor segment through are connected through the magnetic resistance rotor connection segment. The inner wall of the stator yoke is fixedly connected with the two stator cores at intervals. The stator winding is arranged on the inner sides of the two stator cores. The stator exciting winding is arranged between the two stator cores and corresponds to the magnetic resistance rotor connection segment in the height direction. The two stator cores correspond to the magnetic resistance rotor first segment and the magnetic resistance rotor second segment respectively in the height direction.