【Objective】Pine wood nematode (Bursaphelenchus xylophilus) typically live in dark environments and are extremely sensitive to light, exhibiting a strong avoidance response. By studying the inhibitory effects under different light conditions on their population growth, key mechanisms of how light affects the growth of B. xylophilus populations can be revealed. This research also aims to elucidate the underlying mechanisms that inhibit population growth, laying a solid foundation for future optical and basic biological studies on pine wood nematodes and providing new perspectives for their control.【Method】Five light wavelengths (clours)—green, yellow, red, white and blue—were employed to investigate the effects of various light conditions on the nematode population. Additionally, the effects of different blue light intensities on egg hatching rate, sex ratio, body length, and embryonic development were further explored.【Result】Blue light exhibited the strongest inhibitory effect on B. xylophilus, significantly suppressing population growth. Further research on the effects of different blue light intensities on reproductive behavior showed that when the light intensity is below 1 000 lx, blue light has no significant effect on reproduction. However, when the intensity increased to 1 250 lx, compared to the control group, the number of offspring, egg hatching rate, developmental speed, and individual size of the nematodes significantly decreased. Additionally, there are notable changes in the male-to-female sex ratio.【Conclusion】In summary, blue light at intensities above 1 000 lx significantly inhibits the egg hatching rate, developmental progress, and adult body size of B. xylophilus. As an important environmental and physical factor, blue light can influence microbial life cycles, morphological changes, and gene expression, thereby regulating its physiological and metabolic processes.