In this paper, a theoretical model on LD unidirectional side-pumped laser module has been constructed. Combining ray tracing and finite element simulation method, these calculation formulae on pump efficiency and distribution uniformity of light field in the crystal were derived. The effects of LD tangential displacement, radial angle deviation and crystal absorption coefficient on the pump efficiency and the uniform distribution of pump light in the crystal were also numerically analyzed. The results show that, with the increase of absorption coefficient, the distribution uniformity of light field in the crystal will decrease gradually. Maximum pump efficiency up to 93% can be achieved by optimizing the deviation of LD displacement and radial angle. The research results have certain reference value for optimization design and experimental study of the high power LD unidirectional side-pumped laser module.