Abstract: The Cathaysian old land proposed by A.W. Grabau was a old land located to the southeast of Cathaysian geosyncline during Siulian to Jurassic from central-east Guangdong and Fujiang provinces to south east Zhejiang Province and their off shore East China sea Yellow sea extending to southeast Japan and southeast tip of the Korian peninsula. It was an old land belt higher than the sea level as a source area of the clastic materials of the sediments of Simian and Lower Paleozoic strata in Cathaysian geosyncline. The term Cathaysian old land proposed by A.W. Grabau 84 years ago resuted in very important and great effect to the research on geology and tectionics of China. It is a structural unit term suggested in the geosyncline theory framework with some paleogeographic significance as well, base on the research methods of paleotonogy, stratigraphy division correlation and its thickness analysis, sedimentary, stratigraphical contact relationship, which were advanced geological methods in 20’ of last centenary. The research work consequently experienced geosyncline theory period and plate tectonic theory period. There existed some important changing of concept of the Cathaysian old land during the geosyncline theory period, for example, T. K. Huang (1945, 1960) suggested the Cathaysian old land equivalent as the Caledonian folded belt or Cathaysian fold belt which occupied the main area of Kwangdong, Fujian, Jiangxi, provinces and part of Hunan, Zhejiang provinces in south China. Starting from the 90’ of last centenary the research on the Cathaysian old land entered the plate tectonic theory period, and the term Cathaysian old land or Cathaysian block became mainly the continental crust mass, almost totally separated from the concet of Grabau’s Cathaysian old land based on the tremendous new dada and evidence by modern methods such as SHIMP U-Pb, LA-ICPMS U-Pb, 40Ar-39Ar precise age determination, duetile and britle deformation, and deep setting structure. Some intension of the term Cathaysian block in the recent magazines is not that of the original Cathaysian old land. The changing of the concept of the Cathaysian old land reflects one aspect of the advance of the tectonic research work in China.