Human chorionic gonadotropin, or HCG for short, has a normal level of less than 10 mIU/mL and is mainly used clinically to detect pregnancy. Pregnancy is usually accompanied by a rapid increase in HCG level, but the increase and decrease of HCG can also be seen in abnormal conditions, which need to be judged in combination with the specific performance of the patient, HCG value and pelvic ultrasound results. HCG values are different for different weeks of pregnancy, and HCG multiplies every 48 hours during early pregnancy. If the increase is not obvious, there is a possibility of embryonic abortion. If the HCG is below 10,000 IU/mL on day 45 of pregnancy, it is recommended to check progesterone as well as ultrasound to clarify whether the pregnancy is ectopic. If the HCG decreases significantly with the growth of the gestational week, and the ultrasound shows no gestational sac in the uterine cavity, it should be considered that there may be preterm miscarriage or biochemical pregnancy, and the pregnant woman should undergo fertility preservation treatment or uterine clearance surgery under the advice of the doctor. HCG can be produced by tumors of the lung, adrenal gland and liver, so we need to take into account the patient’s specific symptoms and relevant test results to identify the cause and provide targeted treatment.