We have explored the effect of shear force on aggregate size, the secondary structure of proteins, and the viscosity of protein bovine serum albumin solution. The size of protein aggregates and secondary structures of the protein are dependent on the external variables such as temperature, the magnitude of shear, time of shearing, and process of applying shear. The process of application of shear, which can be continuous or intermittent periodic stoppage, can control the characteristics of aggregates of BSA. The viscosity of the protein solution is expected to depend on the size of the aggregates. We have proposed a mechanism of the association of BSA molecules leading to the formation of aggregates. Small aggregates at 40 degrees C are formed through the interaction of side chains, while bigger aggregates formed at 60 degrees C through beta-sheet interaction. The indication of the opening of the BSA molecules at an intermediate temperature is confirmed by the appearance of more side chain and random coil. The shear leads to a highly anisotropic structure at a temperature beyond 60 degrees C and leads to the higher hydrodynamic radius. This makes the solution to undergo transition from dilute to semi-dilute regime and increase in viscosity by a factor fourfold. Subsequently, we have shown that the viscosity depends on the proportion of beta-sheet within the aggregate.