SG-III power laser facility includes many large aperture optical modules, and it is a huge technical challenge to accomplish precise collimation of those units. A comprehensive error analysis methodology based on integrated light propagation theory, numerical calculation, engineering experience is proposed. Firstly, light transmission function with angle error in each mirror is built up, and the main influence factors are analyzed by means of error theory. Thus error decomposition in each light axis of optical module is employed in according with practical situation. Secondly, light axis materialization and homogeneous matrix transformation methods are utilized to depict the relationship of module, light axis, mirrors in one coordinate system，then the design of collimation stage is accomplished with the help of laser tracker. Finally, a assembling stage of typical module for collimation is set up and validated the proposed methodology which is extremely helpful to study the precise collimation technology in high power laser system.