The invention relates to a gravity generator or system installed on a device with wheels. The gravity generator or system comprises a main shaft which is provided with a stress helical-tooth barrel and a hub, wherein the stress helical-tooth barrel is connected with the main shaft through a bearing. The hub is directly connected to the main shaft and is provided with a generator shell, a generator coil is arranged in the generator shell, and a magnetic core is arranged on the stress helical-tooth barrel. An oil cylinder is arranged on the hub and is composed of an oil cylinder piston and an oil pressure driving box. A movable pushing claw is arranged at the tail end of the oil pressure driving box, and the movable pushing claw is matched with the stress helical-tooth barrel. A stress plate is arranged at the tail end of the oil cylinder piston. In the operation process of the device with the wheels, due to the weight of the device, downward pressure is inevitably generated and acts on the wheels, part of the wheels deform to some extent, and energy is recovered by using the pressure to generate deformation. The energy of the part is collected through a recovery and conversion device for subsequent operation of the device.