本文使用乾點式超音波試驗儀，以不同入射角量測天然岩石之超音波速，並針對具葉理之天然片岩以波速極座標圖呈現不同葉理夾角之波速異向性。參數研究方面，以不同波速、厚度互層排列方式作為參數變因，引用司乃爾定律(Snell’s law)計算不同模型葉理夾角之波速，以了解各項變因對波速極座標圖之影響。最後，本文以層狀互層材料模擬天然片岩之波速極座標圖，擬根據研究結果，探討葉理岩石波速異向性之成因及機制。 ;The compositions, arrangement and mineral crystal orientation of rocks are affected by precipitation, earth stress or temperature... physical and chemical reactions during the diagenesis process. Hence, the mechanical behaviors (i.e. strength, elastic modulus, Poisson′s ratio…) usually accompany anisotropy properties, such as: schist or jointed rock mass. For geotechnical engineering, the rock mechanical anisotropy plays an important role for tunnel, slope designs, and their constructions. Non-destructive ultrasonic testing can evaluate strength and deformability of rock material, which provides in-situ judgment basis. This paper presents Snell’s law to investigate wave propagation behavior of anisotropic rocks. This paper analyzes P-wave anisotropy of natural rocks from previous studies, and observes 3 different shapes of P-wave anisotropy, includes circular, ellipse, dumbbell-shaped, eye shape. Parametric study is addressed for determining the shapes of P-wave anisotropy. Finally, this paper will clarify the cause of P-wave anisotropy according to the parametric study.