Our previous work demonstrated that an optical coherence tomography (OCT) technique was able to characterize the whole blood coagulation process. The 1/e light penetration depth (d 1/e ) derived from the profiles of reflectance versus depth was developed for detecting the whole blood coagulation process in static state. To consider the effect of blood flow, in the present study, d 1/e versus time from the coagulating porcine blood circulated in a mock flow loop with various steady laminar flows at mean flow speed in the range from 5 to 25 mm/s . The variation of d 1/e was used to represent the change of blood properties during coagulation in different hematocrits (HCT) ranging from 25% to 55%, velocities from 5 to 25 mm/s , and tubing sizes from 0.9 to 2 mm. The results showed that there were positive correlations between coagulation time (t c ) and HCT, velocity, and tubing size, respectively. In addition, the coagulation rate (S r ) was decreased with the increase of HCT, velocity, and tubing size. This study testified that HCT, flow velocity, and tubing size were substantial factors affecting the backscattering properties during flowing blood coagulation. Furthermore, OCT has the potential to represent the process of flowing blood coagulation with proper parameters.