Abstract: Objective: To investigate the effects of low molecular weight heparin on kallikrein level in patients with preeclampsia. Methods: Ninety-six patients with preeclampsia were divided into the observation group and control group by random number table method(48 cases each group). The control group were treated with conventional therapy, the observation group were additionally treated with 0.3 to 0.4 mL of low molecular weight heparin by subcutaneous injection based on the conventional therapy, once a day, up to before 12 to 24 h of delivery. The blood pressure, 24 h urine volume, urine protein quantity, blood platelet, coagulation function, maternal and neonatal outcomes and pregnancy outcome and kallikrein expression between the two groups were compared. Results: After the treatment, the systolic pressure, diastolic pressure and urine protein quantity in observation group were obviously lower than those in control group(P<0.01). The 24 h urine volume in observation group was obviously higher than that in control group(P<0.01). The differences of the blood platelet, fibrinogen, prothrombin time and thrombin time between two groups were not statistically significant after treatment(P>0.05). The D-dimer level in observation group was obviously lower than that in control group after treatment(P<0.01). The gestational age, neonatal birth weight and prolonged pregnancy time in observation group were obviously higher than those in control group after treatment(P<0.01). The kallikrein levels in the blood, placenta and urine in observation group were obviously higher than those in control group after treatment (P<0.01). Conclusions: The low molecular weight heparin can effectively enhance the kallikrein level in patients with preeclampsia, and improve the maternal and neonatal outcomes.