For aircraft with more fuel quantity in the wing tank, imbalance of fuel delivery between left and right wing tanks affects control and even flight safety of aircraft. Aimed at the problems that ground crew generally have lack of fault diagnosis methods of wing tank transportation imbalance in aircraft maintenance, the fault diagnosis methods based on fuel quantity interval estimation are studied. The regression equation between the left and the right wing tanks fuel quantity is obtained by using the existing flight data, and the estimation interval of the individual value of wing tanks fuel quantity is obtained, which is used as the normal distribution interval of the wing tanks fuel quantity and fault detection method after being modified. By setting reasonable fault judgment conditions, the fuel delivery imbalance fault of left and right wing tanks can be realized effectively. The results show that the method can accurately detect the imbalance fuel delivery fault of aircraft’s wing tanks and reduce the failure rate when flying again. At the same time, the method is easy to realize without adding software and hardware, can be quickly used among ground crew, and has a certain application prospect.