Objective To explore the orientation relationships and changing rules of pedicle screw entry point (PSEP) on the posterior bony landmarks in middle-upper thoracic vertebrae in adults by measuring parameters of 3-D reconstruction CT images. Methods CT images of the middle-upper thoracic vertebrae from 30 healthy adults were used for 3-D reconstruction to observe the anatomical characteristics of posterior bony landmarks, including transverse process-lamina concave, superior ridge of transverse process and outer edge of the lamina. The following basic parameters, including PSEP-to-midline distance (PMD), transverse process-lamina concave-to-midline distance (CMD) and half lamina width (HLW), and target parameters, including PSEP-to-transverse process-lamina concave distance (PCD), entry point location ratio (EPLR) and PSEP-to-superior ridge of transverse process distance (PRD) were determined on reconstructed CT images from T₁ to T₁₀. The differences of bilateral measurements of all parameters and the differences of basic parameters were analyzed, and the changing rules of target parameters measurements from T₁ to T₁₀ were summarized. Results The transverse process-lamina concave, superior ridge of transverse process and outer edge of the lamina of middle-upper thoracic vertebral characterized by obvious and constant anatomical marks with less proliferative. The left and right PMD, CMD, HLW, PCD, EPLR, and PRD were (14.14±2.63) mm and (14.59±2.58) mm, (10.45±2.12) mm and (10.51±2.02) mm, (16.30±1.48) mm and (16.39±1.61) mm, (4.56±1.03) mm and (4.47±0.94) mm, 0.35±0.26 and 0.33±0.30, and (-1.62±1.90) mm and (-1.63±1.44) mm, respectively. There was no significant difference in the measured values between the two sides of the above parameters (P>0.05). Except that the difference between PMD and HLW in T₂ was not significant (P>0.05), the differences between basic parameters in the other segments were statistically significant (P<0.05). PCD of T₁ to T₁₀ showed a trend of decrease first and then significant increases in T₁, T₂, T₉, and T₁₀ compared with in T₃-T₈ (P<0.05). EPLR of T₁-T₁₀ showed a trend of increase first and then decrease, in which EPLR in T₁, T₂ and T₃ were significantly lower than in the following any segments (P<0.01), and in the T₄-T₆ and T₁₀ were significantly lower than in T₇-T₉ (P<0.01). PRD of T₁-T₁₀ showed a trend of increase first and then decrease, in which the PRD in T₁, T₂ and T₃ were significantly lower than in the following any segments, and in the T₄-T₆ were lower than T₇-T₁₀ (P<0.01). Conclusion There is constant orientation relationship and changing rules of PSEP in the middle-upper thoracic vertebrae on the posterior bony landmarks, such as transverse process-lamina concave, superior ridge of transverse process and outer edge of the lamina, and it can serve as a new clinical choice.