To optimize the industrial cultivation model of Caulerpa lentillifera, this study investigated the effects of light quality on its yield traits. A recirculating water system was employed to simulate industrial cultivation conditions. White light served as the control group, while red light (620~630 nm), green light (520~530 nm), and blue light (450~460 nm) were usedas the treatment groups. The light intensity was set at 35 μmol·m^-2·s^-1, with a photoperiod of 12 h of light followed by 12 h of darkness. After 15 days of cultivation, the yield traits of the algae were assessed. The results revealed significant morphological changes. Under red light, the density of newly formed upright branches was (0.51±0.35) pcs/dm, and the density of spherical branches was (0.69±0.20) pcs/mm. Both values were significantly lower than those recorded under white light, which were (1.39±0.39) and (1.14±0.29) pcs/mm, respectively. Furthermore, the proportion of malformed spherical branches originating from creeping branches under red light was 46.7%, which is 6.97 times higher than the malformation rates observed under blue and green light (both 6.7%). The growth rate of newly formed upright branches under green light was (0.23±0.10) cm/d, significantly higher than the growth rate of (0.15±0.06) cm/d under white light. However, the density of spherical branches under green light was (0.66± 0.21) ind/mm, significantly lower than that under white light. This suggests that green light promotes the elongation of upright branches while inhibiting the formation of spherical branches. No significant differences in morphological traits were observed between blue light and white light treatments. In terms of growth rates, no significant differences were found among the red, green, blue, and white light treatments. Regarding pigment content, chlorophyll a and carotenoid levels were significantly higher under green light compared to blue and red light. However, no significant differences were found between red, blue, green, and white lightfor these pigments.Transcriptomic sequencing of C. lentillifera samples under different light conditions revealed several key findings. Under blue light, the number of differentially expressed genes was relatively low. In contrast, green light influenced various metabolic pathways, including riboflavin metabolism and glycolysis/gluconeogenesis. Notably, under red light, the expression of multiple ribosomal protein genes associated with plant morphology was significantly upregulated. Additionally, genes such as g7917 (Maf1) and g8031 (Microtubule-severing AAA ATPasee), exhibited differential expression patterns distinct from those observed under blue light. These differences may contribute to the abnormalities in upright branches and the increased malformation rate observed under red light.In summary, exposure to red light alone inhibits the formation of upright and spherical branches while increasing the rate of malformations. Green light suppresses the formation of spherical branches. In contrast, algal samples treated with white and blue light exhibited better overall yield traits, indicating their suitability for future cultivation systems. This study provides valuable scientific insights for the establishment of monochromatic light regulation strategies in the industrial cultivation of C. lentillifera.