Quality of milk after its packaging is damaged or unsealed is a great problem. Storage quality of milk was studied based on the electronic nose. Firstly, the samples of milk were measured by a gas sensor array, and different dynamic response values corresponding to the response times of 50, 100, 150, 200, 300, 400, 500 and 600th seconds were selected as the test samples. With the help of principal component analysis (PCA) and Fisher discriminant analysis (FDA), the change of milk quality was explored along with the increasing days of storage. At the same time, the preferable analysis range of dynamic response of the array was given, namely the 300~ 600thsecond. Secondly, the mean values of dynamic response values of the range were also selected as representative results of the test samples, and the PCA and FDA were carried out respectively. The results showed that the two representative methods of the samples could discriminate the change of milk quality by PCA and FDA. So it is an effective method to analyze the change of milk quality in condition of non-encapsulation with an electronic nose.