Based on the double beam interference theory and Wiener-Khinchin theorem, the coherence equation of broad spectrum light source was derived and analyzed. In the mixed sequence mode of optical design software Zemax, a coherence function test system of broad spectrum light source was established. The reference light path and the measuring light path were simulated by multi-configuration editor. Collimation system was simulated individually, and the system’s collimation degree achieves the best result by optimization. According to theoretical models, the effects of the fiber core size and alignment error on the collimation degree of collimation system and the coupling efficiency of the whole system were analyzed. Finally, the changing curve was drawn with the origin software.