In the 3rd year of Xing-ding for Xuanzong emperor of Jin dynasty （ 1219 A. D. ） , a strong earthquake occurred at today＇s south part of Ningxia Hui Autonomous Region, China. The number of earthquakes, mainshock time, and the epicenter, which are provided by different documentary records, are very different. Based on the earthquake history data, combined with the inscriptions and the local records found recently in Guyuan county, this earthquake is restudied in this paper. By textual research, the earthquake occurred about 10 o＇clock, Aug. 6 in 1219, the epicenter is on the south of Guyuan （35.6°N 106.2°E） , the magnitude is 6 1/2, and the epieentral intensity is from Ⅷ to Ⅸ.