The influence of the fuel tank arrangement and the refueling sequence on the weight and the center of gravity of civil aircraft are introduced, and the factors of rotor failure, inert fuel tank and structural fatigue which must be considered are illuminated when the fuel tank is designed; Three kinds of fuel tanks with different arrangement and same sequence are put forward . The balance effect of the outer tank fuel to the lift and the changes of center of gravity during refueling are analyzed. This paper gives examples to analyze the loading limit in the condition of three kinds of fuel tanks and offers some references to select the arrangement of fuel tank and the refueling sequence.