The invention provides an oil tank capable of realizing any resting position back-feeding outer bearing force. An first hydraulic channel and a second hydraulic channel which are individual are radically processed on a piston, the end, close to a rod port, of the first hydraulic channel opens, and the end, close to a head port, of the second hydraulic channel opens; a hydraulic valve with the maximum stroke is installed in the first hydraulic channel, a hydraulic vale with the minimum stroke is installed in the second hydraulic channel, the hydraulic valve with the maximum stroke ejects out through a guiding sleeve, and the hydraulic vale with the minimum stroke ejects out through the tank bottom. According to the oil tank capable of realizing any resting position back-feedingthe outer bearing force, contacting force between the piston and the guiding sleeve andbetween the piston and the tank bottom during the maximum stroke and the minimum stroke can be removed, and thus the outer bearing force can be fed back in any resting position through the oil tank. The oil tank is equivalent to installing two limit devices at the two limit points of the maximum stroke and the minimum strokeof the oil cylinder, thus when the oil tank normally works, the piston cannot make a direct contact with the guiding sleeve or the tank bottom.