Objective:To study the expression of Pleiotrophin and Midkine protein in endometrium of endometriosis and its clinical significance.Methods:Expressions of Pleiotrophin and Midkine protein were examined by immunohistochemical staining method in 30 endometrial samples of endometriosis(study group) and 29 endometrium of uterine fibroid(control group).Result:Pleiotrophin protein mainly expressed in the membrane and plasma of glandular epithelium of endometrium.Midkine protein mainly expressed in the plasma of grandular epithelium of endometrium and expressed in nuclei in some samples.The expression of Pleiotrophin and Midkine protein in endometriosis was significantly higher than that in the control group(P<0.001).Conclusions:over-expression of PTN and MK protein in endometrium of endometriosis correlated to endometriotic cell angiogenesis.The change of PTN and MK expression in endometrium of endometriosis may relate to the pathogenesis of endometriosis.