To study the influences of different treatment timing of antisyphilitic therapy of pregnant women on their pregnancy outcomes, and to analysis the related factors. Methods: The clinical data of 125 pregnant women with syphilis between December 2018 and May 2020 were collected retrospectively. The antisyphilitic infection of these women was treated by G240 U benzathine penicillin. These women were divided into group A (31 women with antisyphilitic therapy during <13 gestational weeks), group B (35 women with antisyphilitic therapy during 13 to 28 gestational weeks), group C (48 women with antisyphilitic therapy during >28 gestational weeks), and group D (11 women without antisyphilitic therapy). The adverse pregnancy situations and the influence factors of adverse pregnancy outcomes of the women were compared among the four groups. Results: There were no significant differences in the incidents of preterm birth, stillbirth, abortion, and low birth weight of the women among the four groups (P>0.05), but the incidences of congenital syphilis in group A, group B, group C, and group D were 6.5%, 31.4%, 31.3%, and 9.5%, respectively, which had significantly different among the four groups (P<0.05). Binary logistic regression analysis showed that the main risk factors of severe adverse pregnancy outcomes of the pregnant women complicated with syphilis included their frequent unsafe sex life before pregnancy and their low immunity, and Kendall's correlation coefficient of the severe adverse pregnancy outcomes of the women with their frequent unsafe sex life before pregnancy and their low immunity were 0.198 and 0.262 (P<0.05). Conclusion: Different treatment timing of antisyphilitic therapy of the pregnant women influence their pregnancy outcomes and the early antisyphilitic therapy is better than late antisyphilitic therapy, which suggests it is necessary to screen pre-pregnancy syphilis, and early detection and early treatment of pregnancy complicated with syphilis of the pregnant women should be conducted.