Leak detection of oil pipelines is an important issue for safe operation of pipelines, reducing oil loss and environmental pollution. A new approach based on principal component analysis (PCA) method to detect leaks of oil pipelines is proposed in this paper. In order to detect leaks, a classifier is designed to recognize negative pressure wave curve by training set. Results indicate that the method can detect many leak faults from a pressure curve, which might not be effectively detected by a traditional signal processing based method but can be recognized easily by human visual perception.