Abstract: 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-PGF,. 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 retinopathylgroup 3. 40 cases with hyperplasia type of retinopath; group 4: 40 cases normal controls). Results The results showed that ET increased progressively (P<0. o1) 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.