Based on the law of refraction in vector form, the laser beam propagation in an aspheric and asymmetrical laser beam collimation system from high-power semiconductor laser has been researched for spatial laser beam long-distance propagation. The matrixes transfer formulas for spatial rays have been obtained. For the high-power semiconductor laser with line emitting source, the divergent angle of the converted laser beam has been diminished by the optimization design of high precision collimation system. Cassegrain optical antenna has been designed by optical design software CODE-V to collimate the laser beam further. Based on the two-point algorithm, the divergent angle for the collimation system has been measured. The measured results indicate that the divergent angle of the optimization collimation system is less than 1.924 mrad, and the divergent angle collimated by the optical antenna is less than 96.2 μrad. The spatial rays method possesses reference meaning for accurate counting of complex optical systems. The collimation system designed for high-power semiconductor laser with line emitting source can be widely used in long-distance spatial laser communication.