Preterm birth (PTB) is defined as birth before 37 weeks' gestation, accounts for 6–10% of all births and is a major contributor to neonatal and infant morbidity and mortality The aim of the current study is to assess the diagnostic accuracy of Beta-subunit of human chorionic gonadotropin (β-HCG) in cervico-vaginal secretion, as a biochemical predictor of preterm labor. A cross sectional study was conducted on(100) women between 24th -36th week of singleton pregnancy. The gestational age was determined by the first day of last menstrual period and confirmed by ultrasound, cervi-covaginal secretion samples was obtained through speculum examination from all the patient, the swab disposed of the sample was quantitatively tested for the level of beta-HCG, the level of beta HCG was measured by the radioimmunoassay method using a commercial kit, and the result was reported in milli-international units per milliliter, the results revealed that there was significant difference between both groups regarding S/D ratio of beta HCG (66.97- 21.45) as range S/D for preterm group was higher than full term group the qualitative test was found to have sensitivity, specificity, PPV, NPV and diagnostic accuracy to predict PTB of 68.33%, 96.06%, 75.93%, 94.35% and 91.79%,respectively, It was found to be more sensitive in the high-risk patients, but more specific in the low risk control group.