Based on the phenomena of double refraction and double reflection in crystals,phase characteristics of p-polarized light reflecting and refracting at the boundary between an isotropic and a uniaxial crystal are studied by numerical evaluation.Results show that the direction of optical axis has important influence on phase properties.When light is incident from an optically thinner isotropic medium upon a crystal,the direction of optical axis affects the phase shift of reflected p-polarization light but has no effect on the phase of refracted light.When light is incident from an optically denser isotropic medium upon a crystal with the incident angle less than angle of total reflection,the direction of optic axis affects both the phase shift of reflected and refracted p-polarization light.If the incident angle is larger than critical angle,the optical axis has influence on the curve of phase change of reflected p-polarization light.For the case of light enters into an optically thinner isotropic medium from a crystal with the incident angle less than angle of total reflection,the direction of optical axis will change the way of phase shift of reflected p-polarization light.And the refracted p-polarization light undergoes a phase shift near the Brewster’s angle when the angle between the optical axis and crystal boundary is small.After the incident light is reflected totally,the curve of phase change of reflected p-polarization light varies with the direction of optical axis.