T1 relaxation time for myocardial tissue represents a biomarker for a variety of pathologies. High resolution and pixel-wise T1 mapping can be acquired with Modified Look-Locker Imaging1 (MOLLI). Besides, T1 measurements of blood can be used as a reference value to calculate function parameters like extracellular volume (ECV) fraction2,3 and myocardial blood volume4.5 (MBV). Blood flow may affect blood T1 measurements and cause further deviation in calculating function parameters 6. In our work, we proposed a MOLLI-based flow model to simulate flow effect. Substantial T1 deviation may happen when the spin replacement rate is between 0.65 and 0.70.