An improved winding base structure of a transformer is assembled by combining a primary-side winding base and a secondary-side winding base. The selection of the material of the primary-side winding base and the secondary-side winding base is dependant on the compression-resistant capability because the primary-side input and the secondary-side output of the transformer bear different voltages. The outside of the assembled winding base is disposed with grooves in which the wires are wound, and the center of the winding base is disposed with a through hole for an iron core to be put therein to form a transformer. The sectional winding base of the subject application is characterized in that the primary-side winding base is made of lower compression-resistant material and the secondary-side winding base is made of higher compression-resistant material. Therefore the production cost of the winding base is reduced.