Using the Maxwells equations, we carry out theoretical analysis on the maximum incident and refractive angles at which negative refraction can be realized at the interfaces associated with conventional uniaxial media. In the numerical analysis, the largest incident and refractive angles at which refraction arises are obtained by optimizing directions of the optical axis of the uniaxial bicrystal. Meanwhile, the optical parameters of the ordinary uniaxial bicrystals (including homogeneityjunction and heterogeneity-junction) are given, and some representative laser wavelengths, the largest incident and refractive angles are obtained. The relation between the largest incident angles (or refractive angles) and refractive index is also discussed.