The invention relates to an oil tank of a caterpillar track travelling hydraulic support, mainly comprising a main oil tank, a left oil tank, a right oil tank, a low-order oil absorption tank, an oil absorption filter, an oil return filter, an air filter, a liquid level and liquid temperature meter, a liquid level sensor, a temperature sensor, an oil drainage port, an oil tank cover and a shield.The oil tank of a caterpillar track travelling hydraulic support is in an I-shaped welding structure totally, and utilizes the efficient space of a base seat of the hydraulic support. The main oil tank, the left oil tank, the right oil tank and the low-order oil absorption tank are arranged in the base seat for carrying out filtering and air filtering. The low-order oil absorption tank adopts a low-order form centre to absorb oil, which is safe and stable. The oil storage capacity of the hydraulic support is enhanced, and the oil storage capacity is increased by twice to three times than the oil storage capacity of the traditional oil tank. Therefore, the travelling operation time of hydraulic mechanisms and power mechanisms is prolonged. The invention is an ideal large-capacity oil tank of the hydraulic support.