Abstract: In order to have a clearer sense of the transformer winding deformation, it is necessary to detect the axial and radial deformation of windings simultaneously. The paper firstly analyzes the strain distribution regularities of ribbon optical fibers on the windings, according to which the concept of strain vector as well as the decoupling method of axial and radial strain of the windings is proposed. Subsequently, with ribbon optical fibers laid on a 35 kV continuous winding prototype, a test platform is set up. With the help of Brillouin optical time domain analysis technology, the distributed strain sensor is used to measure the axial and radial deformation of the windings, and the relative error of strain vector is within 7.5%. Finally, it is obtained that the axial and radial deflection of the windings and the average strain of the ribbon optical fibers satisfies a quadratic function relationship, i.e. R² > 0.99. The degree of deformation of the windings is predicted using this relationship, with an error of less than 5%. The proposed method could not only detect axial or radial deformation individually, but also derive axial and radial deformations separately when both deformations occur at the same time, which addresses the problem that the axial deformation of windings cannot be sensed effectively and the degree of deformation is difficult to be determined quantitatively, as well as provides a new solution for detecting transformer winding deformation.