This study was aimed to detect maternal serum levels of thromboxane B2 (TXB2) in different durations of pregnancy and explore the predictive value of TXB2 for preeclampsia. By employing a prospective and double-blind study method, 180 pregnant women with previously normal blood pressures during their progestation were included in the study. Peripheral venous blood samples were obtained during 10–14 (period I), 20–24 (period II) and 30–34 (period III) weeks of gestation. Maternal serum levels of TXB2 were measured by enzyme-linked immunoassay. The pathogenetic condition and pregnancy outcomes of these cases were observed. (1) Among the 180 previously normotensive women, ten developed preeclampsia (case group; four severe and six mild preeclampsia). One hundred and seventy remained normal till the end of pregnancy (control group). (2) With development of pregnancy, the levels of maternal serum TXB2 in the 180 cases gradually ascended as seen through the Wilcoxon Signed Ranks Test. There was a statistical significance in maternal TXB2 levels between two different gestational stages (<0.01). (3) The levels of maternal serum TXB2 were slightly higher in the case group than in the control group during period I of gestation, but the difference was not statistically significant (>0.05); the levels of TXB2 were significantly higher in the case group than in the control group during periods II and III of gestation (both <0.05). (3) The best cutoff points of maternal TXB2 were 3750 and 4400ng/mL during periods II and III of gestation by receiver operator characteristic (ROC) curve; and the sensitivity, specificity, positive predictive value, negative predictive value and odds radio of TXB2 in predicting preeclampsia were 80%, 69.5%, 13.3%, 98.33%, 9.11 and 90%, 68.82%, 13.84%, 99.13, 19.86, respectively. Higher levels of maternal serum TXB2 were detected a long time before clinical symptoms appeared. The maternal serum TXB2 after 20 weeks of gestation had predictive value, and the index after 30 weeks was superior to that prior to 30 weeks .