Abstract: The "North China system" is a tectonic system that trends NNW and was widely developed in the North China Block in Cenozoic with the Changping-Weichang area as a type locality. It is also called "Luanhe tectonic system" because about 40 percent of their occurrences are concentrated in the Yixunhe-Luanhe tectonic belt. By an analysis of the accompanying structural features and by referring to stress measurements and focal mechanism solutions,the principal compressive stress responsible for the "North China system" was determined to be ENE-WSW oriented. It is believed that the WSW push by the Pacific Block toward the North China Block met with the resistance of the Qinghai-Tibet Block would produce such a regional stress field in the North China Plain.