Objective To check the neutrophil count and the expression of cell surface adhesion molecule,lymphocyte function associated antigen?1(LFA?1)in peripheral neutrophils in severe preeclamptic patients and normal pregnant women in order to investigate the correlation of neutrophil activation with preeclampsia. Methods Totally 28 pregnant women in the department of gynecology and obstetrics in Shengjing Hospital from No?vember 2013 to January 2014 were included in the study,and divided into the severe preeclampsia group(n=14),and the control group(normal pregnant women,n=14). There was no statistically significant difference in age and gestational weeks between the two groups. The expression of LFA?1 in peripheral neutrophils was detected by flow cytometry in the two groups. Mean blood pressure(MBP)was measured in the severe preeclamptic group,and the correlation of MBP with expression of LFA?1 was analyzed. Results The neutrophil count was 8.40±2.23 ×109/L in the severe pre?eclamptic group,significantly higher than(6.71±1.58)×109/L in the control group,(P<0.05). The positive rate of LFA?1 in peripheral neutrophils was 63.25±38.025%in the severe preeclamptic patients,significantly higher than 8.32±38.65%in the control group(P<0.05). The expression lev?el of LFA?1 in peripheral neutrophils was significantly correlated with mean blood pressure in severe preeclamptic patients(r=0.64,P=0.013). Conclusion The neutrophil count and the expression of LFA?1 in peripheral neutrophils were significantly increased in severe preeclamptic pa?tients compared to normal pregnant women,and significantly correlated with severity of preeclampsia,suggesting that neutrophil activation participat?ed in the pathogenesis of preeclampsia.