The objective of the secondary optical design of a collimating illumination system is to increase the outgoing light intensity and improve flux utilization. In this study, the influence of the source parameters on the illumination performance of pure-refraction-type and total-internal-reflection-type collimating illumination systems are investigated. The expressions for the relationship between the system's outgoing light intensity, flux utilization, source luminous exitance, and light distribution curve index are derived theoretically and verified by experiments. The results show that the system's outgoing light intensity is proportional to the source luminous exitance. For the total-internal-reflection-type collimating illumination system, a small light distribution curve index leads to a higher light flux utilization, larger outgoing light intensity, and wider lighting range compared to those of the pure-refraction-type collimating illumination system. In contrast, a large light distribution curve index leads to a larger outgoing light intensity and better spot slope in the pure-refraction-type collimating illumination system. This conclusion can provide a theoretical basis for matching and optimizing the source parameters and light distribution element structure in the secondary optical design of collimating illumination systems.