In order to evaluate the performance degradation of hydraulic pump quantitatively, a comprehensive evaluation method of Variational Mode Decomposition (VMD) and Support Vector Data Description (SVDD) is proposed. Firstly, the signal was decomposed into Bidimensional Intrinsic Mode Function(BIMF) components of different frequency components by VMD method, and the outliers were removed by SVDD. Then, the SVDD method was trained by the normal samples, the hyper sphere model was obtained, and the distance from each sample to the center of the sphere was obtained. Then the distance from each sample to the center of the ball was transformed into membership degree, as the performance degradation index were uniformly described. Finally, analysis of experimental fault signals of slipper wear and loose slipper of hydraulic piston pump, the effectiveness of the performance degradation assessment method is fully verified.