By selected the double nozzle flapper type electro-hydraulic servo valve as the research object, the electro hydraulic servo valve wear mechanisms and the omega life theory were analyzed respectively. Moreover the contamination wear accelerated degradation testing system according to the test outline was designed. Through the preliminary experiments on electro hydraulic servo valve, the degree of contamination of oil as the testing sensitive stress was determined, internal leakage and pressure gain as the testing degradation parameter. Through analyzing the preliminary experimental results, the test stress level, the stress way and the models of the internal leakage and pressure gain were given. Combining the above analysis results, it has finally given the step stress accelerated degradation testing method of electro-hydraulic servo valve contamination wear. This proposed method can effectively shorten the test time, guarantee for safe and reliable operation of the electro hydraulic servo valve, and has a certain guiding significance to improve its performance.