Tummy pain on the day of ovulation is commonly caused by the following reasons: First, due to the lower abdominal pain caused by the follicular fluid flow to the pelvis after stimulation at the time of ovulation, this pain is a hidden pain, and it often does not affect the normal life, nor does it affect the normal work. Secondly, due to the inflammation of the pelvis itself, after the follicular fluid flows to the uterorectal fossa, stimulating the posterior peritoneum or sacral ligament, it will lead to stomach pain. Third, due to the formation of the corpus luteum after ovulation, the corpus luteum itself will have a small amount of bleeding, due to the pressure is relatively large, the bleeding is relatively large can also lead to lower abdominal pain. Therefore, for the case of stomach pain on the day of ovulation, it is recommended to go to the hospital for ultrasound examination to find out whether there are any abnormalities in the ovaries and pelvis.