The invention provides a novel monocoque bay oil tank of an unmanned aerial vehicle. The novel monocoque bay oil tank comprises a first tank body and a second tank body; the volume of the first tank body is larger than the volume of the second tank body, a pressurization opening and an oiling opening are formed in the upper part of the first tank body, and an oil conveying opening is formed in theright side of the second tank body; a sealing plate is arranged between the first tank body and the second tank body, an oil guiding pipe is arranged on the position, below the sealing plate, in thesecond tank body, and the second tank body communicates with the first tank body through the oil guiding pipe; and a one-way device is arranged at the oil conveying end of the oil guiding pipe. Fuel oil is consumed in sequence, thus control over the fuel oil mass center is convenient, and the flight property of the unmanned aerial vehicle is improved; the oil guiding pipe is arranged in the secondtank body, thus the fuel oil in the first tank body flows into the second tank body conveniently, meanwhile the one-way device is arranged at the oil conveying end of the oil guiding pipe, and thus backflow of the fuel oil is avoided; and a transverse plate is arranged in the second tank body, the situation that the fuel oil at the oil conveying opening is disrupted due to diving or accelerating,and consequently a flight accident is caused is avoided, a one-way device is also arranged in a third tank body, redundant design is adopted, and thus reliability of an unmanned aerial vehicle oil tank system is improved.