Objective　To study the changes of the four active substances endothelin(ET),calcitonin gene related peptide (CGRP),thromboxane B2(TXB2) and 6-Keto-prostaglandin F1α(6-Keto-PGF1α) in plasma when they acted on each other in the formation and development of diabetic retinopathy.Methods　Using the method of radio-immunity,the levels of ET,CGRP,TXB2,6-Keto-PGF1α in plasma were measured in four groups of patients with type 2 diabetes (group 1∶40 cases without retinopathy;group 2∶40 cases with primary retinopathy;group 3.40 cases with hyperplasia type of retinopath;group 4∶40 cases normal controls).Results　The results showed that ET increased progressively (P＜0.01) with the prolonging of the duration of DM and the worsening of retina damage、CGRP showed a decreasing tendency (P＜0.05,P＜0.01) in the advanced stage of DM retinopathy.Rectilinear regression analysis showed that the association of ET/CGRP with TXB2/6-Keto-PGF1α became closer with the worsening of deabetic retinopathy (r=0.44,P＜0.05;r=0.596,P＜0.01).Conclusion　The four active substances acted on each other in the formation and development of diabetic retinopathy.It had a significent meaning in the initial mechanism of DM,in the development of disease and in the direction of medication usage to understand their relationship.