Hardware Trojan (HT) refers to a special module intentionally implanted into a chip or an electronic system. The module can be exploited by the attacker to achieve destructive functions. Unfortunately the HT is difficult to detecte due to its minimal resource occupation. In order to achieve an accurate detection with high efficiency, a HT detection method based on the electromagnetic leakage of the chip is proposed in this paper. At first, the dimensionality reduction and the feature extraction of the electromagnetic leakage sig-nals in each group (template chip, Trojan-free chip and target chip) were realized by prin-cipal component analysis (PCA). Then, the Mahalanobis distances between the template group and the other groups were calculated. Finally, the differences between the Mahala-nobis distances and the threshold were com-pared to determine whether the HT had been implanted into the target chip. In addition, the concept of the HT Detection Quality (HTDQ) was proposed to analyze and compare the per-formance of different detection methods. Our experiment results indicate that the accuracy of this detection method is 91.93%, and the time consumption is 0.042s in average, which shows a high HTDQ compared with three oth-er methods.