To explore the expression trend of ficolin 3 (FCN3) in type 2 diabetes (T2DM) plasma.Two-dimensional polyacrylamide gel electrophoresis (2DE) was used to separate the plasma proteins from T2DM patients and healthy control subjects. MALDI-TOF-TOF was used to identify the differential proteins. Western Blot and enzyme-linked immune response (ELISA) were used to verify the results from 2DE.The experiment on 2DE showed complement C1s subcomponent, complement C3, C9 and FCN3 were up-regulated in the plasma of T2DM patients. The Western Blot results showed that C9 and FCN3 increased in the plasma of T2DM patients with respect to T2DM-free subjects. The experiment results on ELISA showed that the plasma concentration of FCN3 were (50.88 ± 3.85 ) and (36.20 ± 2.75 ) μg/mL (P = 0.0062) in T2DM and T2DM-free, respectively. The plasma concentration of C9 were (26.22 ± 1.43) and (19.23 ± 1.55) μg/mL (P = 0.0022) in T2DM and T2DM-free. FCN3 and C9 were up-regulated in T2DM plasma.FCN3 over-expressed in the plasma of T2DM patients,which activated the complement system in greater degree.