通过几何作图法，分析了光轴取向任意时，光波在两个单轴晶体分界面上的双反射和双折射. 考虑到入射光波、反射光波、折射光波在界面上相位相等和晶体折射率面的定义，采用斯涅尔作图法，直接在图上得到了两条反射光波和两条折射光波. 根据晶体的光学各向异性，进一步讨论了各光波对应的光线方向和振动方向，并通过几何分析，给出了各反射光波、折射光波、反射光线和折射光线位置的一般表达式. 斯涅尔作图法简单直观，可以直接获得光波的方向，结果具有普遍性.

Double refraction and double reflection at the interface of two uniaxial crystals with arbitrary orientation of optical axis are analysed by the use of Snell's graphic method. Considering refractive index surface of uniaxial crystal and equal phases for incident light，reflected light and refracted light at the interface，directions of two reflected waves and two refracted waves can be plotted on the chart. According to the optic anisotropy of crystal，directions of light rays and polarizations corresponding to every light wave are analyzed. Based on geometrical relations of all vectors，expressions of the positions of reflected waves，reflected rays，refracted waves and refracted rays are given. The Snell's graphic method is simple and visual. The formulae are universality.