To detect the expression of ADAM19 (a disintegrin metalloproteinase 19) in the placenta and peripheral blood and study the correlation between ADAM19 and the pathology of preeclampsia. The patients were divided into the study group (preeclampsia group) and the control group (normal group), and there were 50 cases in the early-onset preeclampsia group, 44 cases in the late-onset group and 50 cases in control group. Venous blood was obtained before childbirth, placental tissues were obtained after delivery. The expression of ADAM19 protein in the placental tissues was detected by immunohistochemistry and Western blot, and that of the plasma was detected by ELISA. ADAM19 protein was detected in the cytotrophoblast cells, syncytiotrophoblast cells, villous stromal cells and capillaries, and the positive signals were localized in the cell membrane and cytoplasm. The expression of ADAM19 protein in the normal placenta was 0.34 ± 0.03, while that of the late-onset preeclampsia group was 0.53 ± 0.02, and that of the early-onset group was 0.82 ± 0.03. And there were significant differences among the three groups (P <0.01). The expression of ADAM19 protein in the plasma of the normal group was (4.52 ± 0.10) μg/L, while that of the late-onset preeclampsia group was (4.32± 0.11) μg/L and that of the early-onset group was (3.78 ± 0.10) μg/L. There was significant difference between the early-onset group and the control group (P < 0.001), also between the early-onset group and the late-onset group (P < 0.001), while there was no significant difference between the late-onset and the control group (P > 0.05). The over-expression of ADAM19 in the placenta of preeclampsia patients may be associated with the occurrence and development of preeclampsia, and ADAM19 may be a marker used for predicting preeclampsia.