Objective To observe the dose-effect relation between excess iodine and coagulation function in rats. Methods Wistar strain rats were divided into four groups: the normal diet and water group(NI), the normal diet and 10-fold iodine group(10HI), the normal diet and 50-fold iodine group(50HI), andthe normal diet and 100-fold iodine group(100HI). Body weights were determined weekly. After 6 months, blood was taken from the eyeball vein and then PT-Time, PT-INR, APTT, TT, Fbg-Time, Fbg-c, AT3:A, and D-dimer were determined by the Sysmex CA7000 automated blood coagulation analyzer. Results PT, PT-INR, Fbg-time, TT, APTT, and AT3: A were decreased while the number of Fbg-c was significantly increased in the 10HI group compared with the NI group(PT, PT-INR, Fbgtime,AT3: A:P<0.05: TT, APTT, Fbg-c P<0.01) PT-time, PT-INR, Fbg-time, TT, and APTT significantly increased while Fbg-c significantly decreased in the 50I and 100I groups comparing with the normal control group (except for Fbg-Time, TT and Fbg-c in the 50HI group P<0.05;the other blood coagulation indexes in the 50?HI and 100?HI groups, P<0.01)Conclusion Appropriate excess iodine can promote blood coagulation of rats, however, with an increase of concentration of iodine, blood hypocoagulability is decreased.