Shear wall systems are one of the most commonly used lateral load-resisting systems in high-rise buildings. Traditionally, high–thickness ratio of RC shear wall is larger than 8. To investigate the seismic performance of a T-shaped shear wall structure, a total of nine 1/2-scaled models were tested under cyclic loading. The variation of high–thickness ratio was from 4 to 9. All models were loaded in the web, except one specimen loaded in the flange. The axial load ratio was in the range from 0.1 to 0.3. The failure process, failure mode and deformation properties of the specimens were presented herein. The test results showed that the T-shaped shear walls had better ductility than traditional RC shear walls. Meanwhile, the ductility of the model did not change consistently with the axial load ratio and high–thickness ratio. Further, the best seismic performance was achieved when the axial load ratio and high–thickness ratio were within a certain range. The ductility and energy dissipation capacity of the specimen with axial load ratio of 0.2 and high–thickness ratio of 6.5 were the best.