Among many factors contributing to fiber optic gyroscope performance, the quality of the fiber coil is one of the most important parts of it. This paper focuses on the disadvantage of cross-layer leap and sensitivity to outside temperature gradient of the present standard quadrupolar (QAD) fiber coil. The paper focuses on reducing the temperature gradient and improving the winding quality of the fiber coil to modify the original standard QAD winding pattern using methods of buffer layers and layer-by-layer leap. The buffer fiber is wound to the inner and outer sides of the fiber coil to reduce the temperature gradient of effective fiber; the layer-by-layer leap is used in place of the original cross-layer leap, and it may reduce bending and stresses variation when fiber leaping. Also, the fibers are arranged orderly to improve the fiber coil winding quality. In addition to building the mathematical model for fiber coil, the simulation and experiment are performed to verify that the improved QAD fiber coils have better thermal performance, and it helps to reduce thermal-induced drift error of a fiber optic gyroscope and improves its precision.