Polycystic ovary syndrome (PCOS) is a common endocrine disorder in women of reproductive age, manifesting as bilateral polycystic ovarian changes with infertility, hirsutism, obesity, acne, menstrual disorders and other symptoms. The main diagnostic criteria for PCOS are: low or no ovulation; clinical or biochemical hyperandrogenism; ultrasound showing ovarian enlargement >10 ml and/or ≥12 follicles of 2-9 mm in diameter. The diagnosis can be made by having 2 of the above 3 items, but congenital adrenocortical hyperplasia, Cushing’s syndrome, and androgen-secreting tumors need to be excluded. According to the diagnostic criteria of polycystic ovary syndrome, the ultrasonographic features are: 1) enlarged ovaries with thick envelope; 2) enhanced interstitial echogenicity, which used to be considered the most sensitive and specific ultrasound sign of PCOS, but this is now controversial; 3) 12 or more small follicles, similar in size and 2-9 mm in diameter, can be detected in the ovaries, and there is no change in the morphology, size and number of follicles under dynamic observation. There was no change in the morphology, size and number of follicles under dynamic observation. The follicles are arranged in a circular bead shape under the ovarian envelope, which is called peripheral follicular type; small follicles are scattered throughout the ovarian cortex in a honeycomb pattern, which is called common follicular type. Small follicles ovulation type] The dominant follicle appears during the follicular phase, but its development is delayed and it ruptures and ovulates when the follicle reaches 14-17 mm in diameter. The signs of ovulation are the same as those of the normal dominant follicle ovulation. The endometrial thickening is not obvious and the ovulation phase is hypoechoic. The “trilineage sign” does not appear and the endometrium shows moderate to strong echogenicity during the luteal phase. The endometrium is the same as that of the small follicle ovulation type.