Abstract: Through the 1:50000 regional geological survey, a new nothosaur fossil site was discovered in Guojiawan area, southwestern Guizhou Province. Based on the field section measurement, the short-distance burial characteristics of the fossils were analyzed in detail, and the age was considered to be Middle Triassic Anisian Stage according to the regional geological mapping and fossil data. Combined with the distribution and the paleogeographic characteristics of the Anisian Stage biotas in the west of Guizhou Province and its adjacent areas, the authors analyzed the possible source. The result shows that Guojiawan area was the possible living place of the nothosaur. The discovery of the nothosaur and its age provides new material and evidence for the evolution and migration of Triassic Marine reptiles, and hence has important scientific significance.