Occurrence of Cracks in the rock mass during underground excavation are influenced by the stress release in the radial direction of the cavity due to excavation and the intermediate principal stress in the drilling direction. Although research using True Triaxial Test system which can control three independent stress directions, to simulate stress changes in the rock mass during excavation, it is difficult to accurately obtain stress values when testing under complex stress paths. In this study, we proposed and conducted a Reduced True Triaxial Compression （RTTC）test using True Triaxial Testing system equipped with a stress compensation to simulate the deformation of rock samples due to stress release. The RTTC test showed that it is suitable for understanding the deformation and crack characteristics caused by stress release, as its failure properties similar to those obtained in True Triaxial Compression tests. Additionally, by using the in-situ stress obtained in the field as the test conditions for the RTTC test, it is possible to evaluate the safety of the rock mass due to static stress changes and estimate the distance from the wall surface where cracks occur.