To establish an animal model of chloasma with kidney deficiency and blood stasis syndrome and to investigate the Lutai Danshen Baishao Formula's effects in replenishing essence and activating blood，and elucidate its underlying mechanisms.Methods:Forty-eight rats were randomly divided into six groups using a random number table：blank control，model，positive drug，and low-，medium-，and high-dose Lutai Danshen Baishao Formula groups(n=8 per group).Except for the blank group，rats were subjected to ultraviolet(UV) irradiation，intramuscular injection of progesterone，and oral administration of hydroxyurea to induce the model.From the first day of modeling，rats in the treatment groups received daily gavage of the respective test formulations.At the end of the experiment，skin and ovarian tissues from irradiated sites were collected for hematoxylin-eosin(HE) staining.The levels of tyrosinase(TYR)，endothelin-1(ET-1)，estradiol(E2)，follicle-stimulating hormone(FSH)，inhibin B(INHB)，and thromboxane B2(TXB-2) were measured.Additionally，malondialdehyde(MDA)，glutathione peroxidase(GSH-Px)，catalase(CAT)，and lipofuscin(LPF) levels were assessed.Western blot was used to detect the protein expression of Kelch-like ECH-associated protein 1(Keap1) and nuclear factor erythroid 2-related factor 2(Nrf2) in the skin to explore the antioxidant and anti-chloasma mechanisms.Results:Compared with the normal group，rats in the model group developed brown，patchy skin lesions.Levels of TYR，ET-1，INHB，TXB-2，MDA，LPF，and Keap1 protein expression were significantly increased(P<0.001)，while E2，FSH，CAT，GSH-Px levels，and Nrf2 protein expression were significantly decreased(P<0.001).These abnormalities were ameliorated in all treatment groups.Conclusion:A rat model of chloasma with kidney deficiency and blood stasis syndrome can be successfully established by combining oral hydroxyurea，intramuscular progesterone，and UV irradiation.Lutai Danshen Baishao Formula exerts its therapeutic effects by modulating the Keap1/Nrf2 antioxidant pathway，inhibiting tyrosinase-mediated oxidation，and improving follicular quality，thereby reducing melanin formation and manifesting the traditional Chinese medicine effects of replenishing essence，activating blood，and eliminating chloasma.