The utility model discloses a supporting device for an oil cylinder, which belongs to the technical field of oil cylinder maintenance and comprises a supporting platform, connecting shells are fixedly connected to two sides above the supporting platform, and electric push rods are fixedly connected to the interiors of the two connecting shells; through the arrangement of the electric push rods, the positioning blocks, the first racks, the gears, the second racks and the bearing plate, when the two electric push rods drive the positioning blocks to move downwards, the first racks can be driven to move downwards synchronously, and when the two first racks move downwards to be meshed with the two gears, the first racks can be driven to move downwards; furthermore, the device can lift and position the oil cylinder at the same time, the situation that the maintenance difficulty is increased due to the fact that the oil cylinder easily shakes in the maintenance process is prevented, meanwhile, the heavy oil cylinder does not need to be manually lifted to the supporting platform to be subjected to the corresponding maintenance process, and therefore the labor consumption can be greatly reduced, and the maintenance efficiency is improved. And meanwhile, the maintained oil cylinder does not need to be manually unloaded, so that secondary labor consumption is avoided.