In recent years, with the advancement of science and technology and the rapid development of animal husbandry economy, the research on bovine B-ultrasound in the examination of dairy cow reproductive organs has also made great progress. At the same time, bovine B-ultrasound diagnostic technology has been increasingly widely used in the diagnosis of reproductive system diseases. Bovine B-ultrasound has the advantages of safety, time saving, non-destructive, easy operation and high accuracy. Bovine B-ultrasound is mainly used for the examination of dairy cow reproductive organs and the diagnosis of reproductive diseases by rectal exploration. Using bovine B-ultrasound diagnostic technology, the anatomical position of the ovary, the contour, diameter, morphology and location of follicular cysts and corpus luteum cysts can be displayed, providing images and measurement data for the diagnosis of ovarian cysts. The B-type instrument used to study various changes in the reproductive organs of cows was developed in the 1980s. Chaffaus S et al. first brought the bovine B-ultrasound probe into the rectum to study the conceptus of 150 cows. Since then, the scope of research has been continuously expanded, the content has been continuously deepened, and rectal probes of different frequencies have been developed. These studies have fully demonstrated the unique effects of bovine B-ultrasound tomography. Ovarian cyst (COD) in dairy cows is one of the ovarian diseases that cause abnormal estrus and infertility in dairy cows. Ovarian cyst refers to a pathological state in which there is a follicular structure on the ovary, with a diameter of more than 2.5 cm, and the existence time is more than 10 days. At the same time, there is no normal corpus luteum structure on the ovary and it is accompanied by abnormal estrus. This disease is generally divided into two types: follicular cyst and corpus luteum cyst. The wall of follicular cyst is thin, and it exists in one or both ovaries in a single or multiple form. Corpus luteum cyst is generally single, exists in one ovary, and has a thicker wall. Both structures are caused by the failure of follicles to ovulate. The former is caused by the degeneration of the follicular epithelium, the hyperplasia and thickening of the connective tissue of the follicular wall, the death of the oocyte, and the non-absorption or increase of the follicular fluid; the latter is caused by the luteinization of the epithelium of the unovulated follicle wall, so it is also called luteinized cyst.