Clomiphene and Letrozole are both drugs for the treatment of infertility, the main difference between the two is that Letrozole can only regulate the body’s estrogen, and Clomiphene can regulate the body’s estrogen as well as enhance the function of the ovaries and luteal insufficiency. Clomiphene, the main ingredient of which is clomiphene citrate, is a non-steroidal agent and anti-hormonal drug with strong anti-estrogenic effect and weak estrogenic effect, which can be used for treating female infertility without ovulation; treating luteal insufficiency; testing ovarian function; and detecting the function abnormality of the hypothalamus-pituitary-gonadal axis of males. It is contraindicated in patients with uterine fibroids, ovarian cysts, and thrombophlebitis. Use with caution in patients with polycystic ovary syndrome. Letrozole, a highly selective non-steroidal aromatase inhibitor, can reduce the body’s estrogen level, thus eliminating the stimulating effect of estrogen on tumor growth. It is mainly used for the treatment of postmenopausal patients with advanced breast cancer who are ineffective in anti-estrogen therapy, and can also be used as adjuvant therapy for postmenopausal patients with early breast cancer. Allergic to the product, severe hepatic insufficiency, children, pregnant and lactating women are prohibited; severe renal insufficiency patients should be used with caution. Both Clomiphene and Letrozole should be taken under medical supervision.