<p>This retrospective study evaluated diagnostic and prognostic values of sFlt-1/PlGF ratio combined with serum endocan-1 for preeclampsia (PE). This study included 105 patients with PE admitted at Xiamen University Affiliated Xiang’an Hospital from January 2020 to September 2023, with 90 healthy pregnant women receiving routine check-ups during the same period as controls. sFlt-1, PlGF, and endocan-1 levels were measured, and sFlt-1/PlGF ratio was calculated. The correlation of sFlt-1/PlGF ratio with serum endocan-1 levels was analysed, and influencing factors for poor prognosis of PE patients were screened. Diagnostic and prognostic values of sFlt-1/PlGF ratio combined with serum endocan-1 were assessed. Results showed an increase in sFlt-1/PlGF ratio and serum endocan-1 levels in PE patients and a positive correlation between them. For assisting in the diagnosis of PE, the AUC of the sFlt-1/PlGF ratio combined with serum endocan-1 was 0.874 (95%CI: 0.819 − 0.917; sensitivity, 75.24%; specificity, 100.00%), which was superior over that of sFlt-1/PlGF ratio (<i>P</i> = 0.025) and endocan-1 (<i>P</i> = 0.047) alone. Elevated sFlt-1/PlGF ratio and serum endocan-1 levels were independent risk factors for poor prognosis of PE patients. For assisting in predicting poor prognosis of PE, the AUC of sFlt-1/PlGF ratio with serum endocan-1 was 0.955 (95%CI: 0.896 − 0.986; sensitivity, 82.61%; specificity, 100.00%), which was higher than that of sFlt-1/PlGF ratio (<i>P</i> = 0.023) or serum endocan-1 (<i>P</i> = 0.010) alone. Altogether, sFlt-1/PlGF ratio combined with serum endocan-1 is advantageous over sFlt-1/PlGF ratio and serum endocan-1 alone for predicting PE occurrence and prognosis.</p>