The application provides a method and device for adjusting blood flow rate under the largest congestion state based on a microcirculation drag index. The method for adjusting the blood flow rate underthe largest congestion state based on the microcirculation drag index comprises the following steps of according to the blood flow rate v, an aortic pressure wave form and physiological parameters, obtaining a microcirculation drag index iFMR in a diastolic phase; if the microcirculation drag index iFMR in the diastolic phase is less than K, then enabling an adjusting parameter r to be 1; and ifthe microcirculation drag index iFMR in the diastolic phase is larger than or equal to K, enabling an adjusting parameter r to be shown as the description, wherein K is a positive number less than 100. For the method disclosed by the invention, according to the physiological parameters, the microcirculation drag index iFMR in the diastolic phase is obtained, then iFMR is compared with K to obtainthe adjusting parameter, and then through the product of the adjusting parameter and the blood flow rate under the largest congestion state, the amended blood flow rate under the largest congestion state is obtained, so that the measuring result is more pointed, the individualization difference is obvious, and the method is more accurate.