Abstract: According to "Historical Records", there existed large amounts of mercury in Qin Mausoleum; nevertheless, over this problem there is still much disagreement among archaeologists. Geochemical and geophysical survey shows that there does exist strong mercury in Qin Mausoleum. A strong mercury anomaly was detected over Qin Mausoleum by mercury vapors survey. If water from the mountain was really used as rivers in Qin Mausoleum as recorded by historical documents, there should exist 300 tons to 2500 tons of mercury in it. Where did these large quantities of mercury from come? The Xunyang mercury deposit could not supply such huge amounts of mercury, and hence the giant geochemical block in Youyang of Chongqing was probably one of the important mercury sources for Qin Mausoleum.