Strong positivity usually appears on the 1st-2nd day of ovulation. Ovulation usually occurs within 48 hours, and the ovulation test paper will become weakly positive after ovulation. The accuracy of ovulation test paper is relatively high, so if women of childbearing age have the requirement of fertility, they can arrange their sexual life according to the test result of ovulation test paper, which is conducive to pregnancy. The principle of ovulation test paper is to measure the level of luteinizing hormone in the patient’s body, and when luteinizing hormone increases to the peak of secretion, ovulation can take place. Usually 1-2 days before ovulation, luteinizing hormone secretion from weak to strong, ovulation test paper shows weak positive gradually become strong positive. After ovulation, the luteinizing hormone in the body decreases, and the ovulation test paper changes from a strong positive to a weak positive. At this time, you should arrange to have intercourse, and the probability of conception within 24 hours is greater. In addition, strong positivity normally occurs on the first day of ovulation, and the egg survives in the body for 24-48 hours, and the sperm survives for 3-5 days. Clinically, body temperature can be monitored, and a 0.2℃-0.5℃ increase in basal body temperature after ovulation can determine whether ovulation has occurred. If ovulation has not been a strong positive, it is recommended to go to a regular hospital for examination.