Light-emitting diode (LED) lighting sources offer significant advantages in terms of lighting quality and energy efficiency. However, their rich blue spectrum can have varying effects on students' learning efficiency, alertness, and attention. In this study, 24 college students were exposed to LED lighting with different illumination levels (300 lx, 1000 lx, 2000 lx) and correlated color temperatures (4000 K, 6500 K) for 50 min through simulated classroom lighting in the laboratory, and the changes in subjective alertness were evaluated by fatigue scale. The results show that under both 4000 K and 6500 K correlated color temperature illumination conditions, increasing the illuminance level can significantly improve subjective alertness, and the alertness is the highest under 2000 lx illuminance conditions. The influence of correlated color temperature on subjective alertness is related to illuminance level. Under low illumination conditions (300 lx), 6500 K color temperature can significantly improve subjective alertness compared with 4000 K. Still, under medium illumination (1000 lx) and high illumination (2000 lx), no obvious advantage of 6500 K correlated color temperature in improving subjective alertness is found.