Objective To study the mechanism of Bushen Huatan Formula（BHF

补肾化痰方） on obese type polycystic ovarian syndrome（PCOS）. Methods SD rats were treated with Letrozole combined high-fat and cholesterol to induce the obese PCOS rat models. A total of 99 successful modeling rats were divided into a model group（n=99）

BHF high dose group（n=20）

BHF middle dose group（n=20）

BHF low dose group（n=20）

and a metformin group（n=20）. Another 23 rats were set as blank group. The BHF low

middle

high dose group was given 16.65

41.63 and 83.25 g/（kg·d） by gastric perfusion

while the metformin group was given metformin 300 mg/（kg·d）

and 5 ml/kg distilled water was given to the model group and the blank group. All groups were treated once a day for totally 21 days. HE staining of ovarian tissue

testosterone（T） and free fatty acids（FFAs） levels of serum were detected by ELISA. The protein relative expressions of NLRP3

apoptosis associated speck-like protein-2 containing a CARD（ASC2）

cysteine-requiring aspartate protease-1（Caspase-1） were detected by Western-blotting. The interleukin-1 receptor（IL-1 R）、nuclear factor-κB（NF-κB） protein positive production were detected by immunohistochemical method. Results Compared with the blank group

model group dominant follicle in the ovary had been absent

meanwhile

the serum T and FFAs in the model group increased significantly

average optical density of IL-1 R

NF-κB in ovarian tissue and expression of Caspase-1

NLRP3

ASC2 protein increased significantly（P<0.05 or P<0.01）.Compared with the model group

expressions of NLRP3

Caspase-1

ASC2 and IL-1 R in ovarian tissue of the BHF high and middle dose group as well as the metformin decreased significantly（P<0.05）. The level of serum T and FFAs in metformin group and BHF high dose group decreased

and the average optical density of IL-1 R

NF-κB significantly decreased（P<0.05 or P<0.01）. There were no statistics difference in expression of Caspase-1

NLRP3

ASC2 protein average optical density of IL-1 R

NF-κB among different dose BHF group and metformin group（P>0.05）. Conclusion The Bushen Huatan Formula can improve obese PCOS by inhibitng the NLRP3/ASC2/Caspase-1 inflammasome signal pathway

and there is no obvious dose-effect relationship in the regulation of pathway.