Objective To explore the potential mechanism of Liangxue Jiedu Lishi Fang（ 凉血解毒利湿方

LJLF） in treating psoriasis. Methods Fifty BALB/c mice were randomized into control group

model group

methotrexate group as well as Chinese medicine high and low dose groups. Group except for the control group was coated with 5% imiquimod cream for 6 days to establish a psoriasis model. Chinese medicine high and low dose groups were respectively given oral LJLF 42 and 21 g/（ kg·d）

methotrexate group was given methotrexate tablets 1 mg/（ kg·d） by gavage and the model group and the control group were given 0. 4 ml distilled water once a day for 6 days. On the 7 th day

the changes of the skin lesions were observed; the morphological changes of the lesions were observed by HE staining and the thickness of the epidermis was measured under light microscope; immunofluorescence method was used to detect the number of proliferating cell nuclear antigen（ PCNA） mitotic cell nucleus

mitotic cell ratio

and the expressions of cortical protein

peroxisome proliferator activated receptor α（ PPAR-α）

peroxisome proliferator activated receptor γ（ PPAR-γ） and peroxisome proliferator-activated receptor β/δ（ PPAR-β/δ） in skin lesions. The mRNA and protein expressions of PPAR-α

PPAR-γ and PPAR-β/δ in mouse skin were detected by real-time PCR and western blot respectively. Results The mice in the model group had squamous skin scales

deep erythema and thick infiltration. Compared with those of the model group

the lesions of each treatment group significantly improved.Compared with those in the control group

the epidermal cell layer in the model group was thicker

the number of mitotic nuclei and the mitotic cell ratio significantly increased. Compared with those in the model group

the expressions of PPAR-α and PPAR-γ protein increased in methotrexate group and Chinese medicine high and low dose groups

while the expression of PPAR-β/δ decreased

and the mRNA levels of PPAR-γ and PPAR-β/δ in methotrexate group significantly decreased

so as the PPAR-β/δ mRNA in high and low dose Chinese medicine groups（ P < 0. 05 or P <0. 01）. Compared with the high dose Chinese medicine group

the expression of PPAR-β/δ mRNA in the low dose Chinese medicine group significantly decreased（ P < 0. 01）. Conclusion LJLF could regulate the expression of PPARs in the skin lesions of psoriatic mice and thus inhibits the excessive proliferation and differentiation of epidermal cells

which may be one of its mechanisms in the treatment of psoriasis.