The four large chunks of grayish-brown jade material found at the northern end of Sanxingdui site have attracted much attention. It is preliminarily inferred that they came from the southern section of the nearby Longmen Mountains, which lacks the support of on-site investigation and scientific identification of jade articles, materials and ores from the origin. This paper discusses and analyzes the origin of large jade materials based on two large chunks of jade material unearthed at Sanxingdui site, fully considering the transport conditions and capacity in antiquity, and integrates it with the geological data and results of mineral resource survey in the Longmen Mountains. Through source investigation method, the composition tracer study of river pebbles was conducted from the close to the distant along the upper reaches of the Yangtze River. After initial identification of the target origin of the jade, groove sampling is conducted for comparative analysis of the rock formations in the target area, river pebbles and ore flakes of Sanxingdui jade materials, in order to find ore belts that match the environment where the jade materials were generated. Source investigation and detailed thin-section identification show that ore from the serpentine mine at Hongyan Mountain in Pengzhou has similar volume and serpentine content with the large jade materials at Sanxingdui, by comparing their mineral compositions, original rock natures, structures, hardness and other indicators, it can be concluded that the original rock of the two large jade materials belong to the serpentine produced in the ultrabasic rock, and the large chunks of jade material at Sanxingdui site originated from the Pengzhou Serpentine Mine.