Abstract: The invention discloses an online diagnosis method for transformer winding deformation position, including: (1) collecting a transformer with known winding state and decomposing into several position sub-samples; (2) performing feature extraction on each position sub-sample with information entropy, adding with label indicating deformation and inputting into support vector machine to train diagnosis model; (3) decomposing a transformer under diagnosis into 9 position subsamples in the way of step (1), performing feature extraction of step (2) and inputting into the diagnostic model trained in step (2); (4) outputting diagnosis result from the support vector machine about whether the position sub-samples of the transformer is deformed.