Abstract: Australia CSIRO hollow inclusion triaxial strain cell possessing many unique merits is one of the most world-wide measuring devices applied for geostress measurements. The measuring technique is discussed. The arranging style of strain gauges and the correcting method used for the measured values of the originally relieved strains by confining pressure tests are introduced. The concrete correcting method of the measured values of relieved strain is advanced, and the measured geostress values calculated by the relieved strains after correction are more accurate. In the dynamic changing measurement of rockmass stress after excavation of the permanent ship-lock of the Three Gorges Project, the errors of the measured values of geostress caused by the errors of arranging places and angles of strain gauges are analyzed, and the measured values of the relieved strains are corrected. Based on the corrected strain values, the measured dynamic changes of rockmass stress are better in accordance with the practical engineering state.