This study investigates the influence of aspect ratio on the mechanical properties, energy dissipation, and failure mode of layered phyllite. Uniaxial compression and split Hopkinson pressure bar (SHPB) tests were conducted on phyllite specimens with varying aspect ratios (L/D=0.5,0.6,0.8,1.0,1.2,1.6,2.0) at four inclination angles(α=0°，30°，60°，90°). Results from static uniaxial compression test reveal that the peak strength and the peak strain of phyllite decrease with increasing aspect ratio at different dip angles. Uniaxial dynamic compression tests show that the dynamic compressive strength of phyllite with four bedding dip angles exhibits a quadratic function relationship with the length-diameter ratio of the specimen under dynamic impact compression conditions. With increasing length-diameter ratio, the dynamic compressive strength reaches a peak and then gradually decreases. The peak strain of phyllite decreases exponentially with the aspect ratio of specimen. Energy analysis of dynamic impact compression test indicates a three-stage change in incident energy, reflection energy, and transmission energy of phyllite under different working conditions, from slow rise to rapid rise and finally to being stable. The reflection energy ratio of phyllite increases first and then decreases with the increase of the length-diameter ratio, while the transmission energy ratio shows the opposite trend. Comparative analysis using the energy ratio method reveals that the reflection energy ratio of phyllite reaches its maximum and the transmission energy ratio reaches its minimum when the aspect ratio is L/D=1.2. Macroscopic failure mode analysis indicates that the aspect ratio significantly affects the macroscopic failure mode of phyllite under dynamic impact compression, with smaller the aspect ratios resulting in more complete fractures and larger aspect ratios leading to less sufficient damage.