Abstract: Kohonen Network (Self-organizing Mapping Model) is applied to aeroengine fault diagnosis.The technique of sequencing diagnostic results and extracting typical samples from sample group is presented.Some examples of application of Kohonen Network to JT9D jet engine fault diagnosis are given.It is shown that Kohonen network is simple to compile program and easy to use,can provide correct diagnostic results for the abnormal samples.Especially it can reveal the statistical characteristics of samples clearly and directly.The method of extracting typical samples from sample group is useful for riving the empirical engine fatult equation.