Palladium (Pd) as a typical high-pressure standard material, studying the structural changes and thermodynamic properties under extreme conditions is widely demanded and challenging. Particularly, understanding the solid-solid phase transition processes of Pd under shock loading is still scarce. In this paper, using the classical molecular dynamics simulations embedded atom method (EAM) interatomic potential, we investigate the phase transition of single crystal Pd from atomic scale under shock loading. A series of structural features are observed in the pressure interval 0-375 GPa. The results suggest that from the initial face-centered cubic (FCC) structure to the stacking faults body-centered cubic (BCC) structure with hexagonal close-packed (HCP) structure, and finally complete melting. Under shock loading of 100 oriented bulk Pd, we find the transformation to BCC structure can take place almost at 70.0 GPa, which is much lower than the previous static calculation results. In addition, we find that the phase transition depends on the initial crystal direction of impact. Under impacts along the 110 and 111 direction, the FCC-BCC phase transition pressures increasing to 135.8 GPa and 165.4 GPa, respectively. Also, the introduction of defects will increase the phase transition pressure of FCC-BCC by 20-30 GPa compared to perfect crystals，Which is verified by the distribution of the potential energy. An interesting phenomenon that reduced FCC-BCC transition pressure of Pd under shock loading was found in this paper, which provides new theoretical insight into the application of high pressure experiments in the future.