Molecular architecture of polymer is very important variable for polymer processing since it controls macroscopic rheological properties of polymer such as viscosity, normal stress coefficients, hydrostatic pressure, and so on. Owing to substantial improvement of experimental and computational techniques, there has been much progress in establishing structure-property relationship of polymer. However, full understanding of structure-property relationship of polymer still has been missing so far. In order to understand structure-property relationship of polymer, we carried out multi-scale simulations at atomistic (NEMD) and mesoscopic (BD) level of description under flow condition. We have tested three types of polyethylene liquids with same molecular weight; linear, Short Chain Branch (SCB), and H-shaped polyethylene. From multi-scale simulations of three types of polyethylene liquids, we found very intriguing results regarding the effect of short chain branching. We proposed new hypothesis regarding the effect of short chain branching on macroscopic rheological properties and confirmed it by comparing multi-scale simulations with experimental results. This understanding of role of branch will be very important factor to produce new final materials simply by changing molecular structure with same molecular weight and to anticipate macroscopic rheological properties of various branched polymer such as star, comb, dendrimer, caley-tress, and so on in the future.