Wollaston prism is used as a polarizer in ArF lithography tool polarization illumination system. Wollaston prism is made of one kind of material used at 193 nm wavelength, the beam separation angle is very small and the prism is very long. In order to solve these practical problems, Wollaston prisms made of positive crystal are analyzed by the law of refraction, and the beam separation angle formulas are derived. A result is presented that the beam separation angle of Wollaston prism made of two kinds of positive crystal is more than that of Wollaston prism made of single positive crystal after analysis and comparison by MATLAB. A Wollaston prism with the beam separation angle of about 10° is designed at wavelength of 193 nm. Another Wollaston prism only with a output beam of linearly polarized light is designed at wavelength of 193 nm. The two prisms are made of positive crystal, the lengths of both the two prisms are medium, which can be used for the polarization illumination system in ArF lithography tool.