Basal body temperature is the temperature of the body in its most basic condition and reflects the level of energy metabolism of the body in the resting state. In the menstrual cycle, the basal body temperature varies cyclically with the amount of different estrogen and progesterone secretion. After ovulation, the progesterone produced by the corpus luteum acts on the hypothalamic thermoregulatory center, causing the body temperature to rise by 0.3-0.5 degrees, which lasts until 1-2 days before the next menstrual period or the first day of menstruation, when the body temperature drops to the original level, and the time of temperature increase should last 12-14 days. Therefore, in a normal menstrual cycle, the basal body temperature measured daily is drawn as a continuous line in a biphasic curve. If ovulation does not occur and there is no corpus luteum formation, the basal body temperature does not rise and change to a monophasic curve. Clinically, this method can be applied to guide contraception and conception, to assist in the diagnosis of menstrual disorders, and to assist in the diagnosis of conception. Women should pay attention to monitoring the basal body temperature, which should be done early in the morning after waking up, without talking or moving, by taking a thermometer and monitoring the body temperature, the time of daily monitoring should be consistent, keep records and make a curve, at the same time, factors that may affect the body temperature should be recorded, such as sex, cold, insomnia, menstrual period, etc. It is usually more meaningful to monitor more than 3 consecutive menstrual cycles.